Holden’s HK-T-G models have long been a beloved part of Aussie car culture. From weather-beaten survivors and chalkmark-correct stockers to tubbed, slammed and repowered street machines and race cars, these three model series have been so popular that it’s hard to imagine a way to build a truly unique one today, 58 years after they first launched.

First published in the May 2026 issue of Street Machine

However, when the covers were ripped off Peter Liversidge’s 1971 HG wagon as part of the Meguiar’s Great Uncover at Street Machine Summernats 38, we all got to see a fresh take on Holden’s mid-range Kingswood. Named ‘Kingsboost’, Peter’s creation packs a plethora of wild body and chassis mods, with details for miles. But its major point of difference undoubtedly comes from the 6.6-litre, turbo-diesel LBZ Duramax donk up front (see more below).

“I wanted to put a Duramax in something; the power and torque out of those engines is amazing,” he says. “I’ve had Silverados and GMCs in the past with these engines, and in a 3.5-tonne truck with a tune, you could fry a set of tyres off them.”

Initially, Peter was going to go crazy and put one of these mills in an HB Torana, but he soon changed his mind. “I build cars to drive, and we couldn’t have got that engineered; that’s why we went with the HG wagon,” he says.

“I named it Kingsboost because it’s just a Kingswood with a bit of boost,” he laughs. “It’s not for any status or unbelievable power, although with 550hp and 921lb-ft of torque, it will pack a bit of neck-snapping punch.”

This isn’t Peter’s first car-building rodeo, but it has definitely been the most intense, all-encompassing project he’s undertaken. Impressively, for a car that wowed the crowds in the Elite hall at ’Nats 38, Peter intends to drive the wheels off the HG once its show days are done.

Peter has had a long love affair with HK-T-Gs, and has an HG Monaro tucked away in the garage keeping Kingsboost company, so it didn’t take him long to settle on a roomy five-door first-gen Kingswood for this build. “I’ve always loved wagons,” he says. “My first car was an HT Premier wagon; I loved everything about it and the memories it helped create.

“I got the HG from the south coast of Queensland. My mate Brian Terry, the mechanic, fabricator, engineer and certified car whiz on the whole project, drove almost 30 hours straight with a trailer to negotiate the deal and bring the ugly duckling home. I’ve gotta be honest — I wasn’t overly impressed when the HG rocked up, but Brian reminded me we were looking for good bones, as that’s probably the only part we’d reuse.”

While we’ve seen all manner of small- and big-block V8s up to 800ci between HK-T-G chassis rails, Peter’s choice of a Duramax led to some fairly intense complications due to its sheer size and 600kg heft with the six-speed Allison transmission attached. He and Brian had to build a complete custom chassis to tie the front and rear of the wagon together, along with fabricated transmission and tailshaft tunnels, rocker panels, a custom smoothed floor, custom wheel tubs, hidden fuel cell and more.

“There were plenty of problems,” Peter laughs. “Firstly, we had to work out if we could even fit a Duramax and Allison in the Kingswood. Driving back from the docks with the motor and gearbox crated up in the back of the ute, we were looking in the rearview mirror at a lump of steel the size of a Morris Minor! Then we had to work out how to fit the rear tyres in without losing the back seat and some of the rear door. Although we lost a bit of the rear cargo real estate, it all looks and works as it should.”

Boasting a big 6.6-litre capacity and a turbocharger from the factory, the LBZ Duramax was fitted to trucks that weigh a full two tonnes more than an HG Kingswood, so Peter chose to keep the mechanical package simple. Still, an improved fuel system, flash-tuned ECU, and Garrett GT37 turbo add up to a healthy 550hp at 35psi, with a world-turning 921lb-ft threatening to twist the 1500kg Kingswood apart.

McDonald Brothers came up with a front end that could handle the massive weight of the engine and transmission, including tubular arms and crossmember, steering rack, and Viking coil-over struts, all of which freed up some extra room. Out the back, a McDonald Brothers four-link rear end replaces soggy leaf springs, and a built nine-inch lives in place of the factory banjo diff.

Once Peter and Brian had the big 6.6-litre donk in the wagon and the chassis engineering was all sorted, their attention turned to the body, which was in very rough shape with every panel scratched and dented. NXT Level Restorations got it all straight and laid down the custom-mixed PPG Bronze Horizon, with gloss for the body and a satin finish underneath and inside.

“Even though it looks fairly standard, there isn’t one square inch that hasn’t been modified, cut-and-shut, reshaped, smoothed, or re-engineered,” Peter says.

The long list of body mods includes a reshaped front valance; smoothed inner guards and firewall; custom cowl plenum; reshaped front wheelarches and guards; custom grille emblems; smoothed and reshaped radiator support; a custom bonnet with a smoothed skin, rolled leading edge and profiled cut-out for the exposed turbo and pipework; hidden windscreen wipers; shaved gutters and mouldings; extended rear wheelarches; shaved bumpers; a Monaro rear beaver panel; frenched AMG exhaust tips; and a smoothed tailgate with hidden hinges.

All that work was rewarded at Summernats 38, come judging time in the Elite Hall. “It had a great reception at Summernats, as we picked up Top Wagon and made the Top 20 Elite,” Peter says. “No one had seen it before pulling it out of the trailer in the Top 60 hall, so there was a huge amount of trust from the Summernats team to let us bring such a unique build. I want to show it off to credit all the guys who also put their skills, creativity, heart and soul into building my dream and turning my ideas into reality. Then I want to drive the wheels off it.”

Having dreamed up such a wild, finely crafted piece of work, you can hardly blame him!

TRUCK YEAH

General Motors launched the Duramax in conjunction with Isuzu in late 1999, as a new-generation, 6.6L turbo-diesel V8 to power their medium- and heavy-duty trucks, vans, and pick-ups. The mills were built exclusively in Moraine, Ohio by the DMAX company, but Isuzu gave up its involvement in the project in 2022, leaving GM as the sole owner.

Production began in 2000 with the LM7, an iron-block design using 32-valve alloy heads rated for 300hp and 520lb-ft. After the LM7 finished production in 2004, the Duramax has evolved through successive generations, just like its LS petrol V8 stablemate, including the LLY (2005-’07); LBZ (2006-’07); LMM (2007-’10); LGH (2010-’11); LML (2011-’16); and the current L5P (2017-present). An updated L5P model was released in 2024, coded ‘L5P Gen2’, while an L5D was run in 2018-’19 in some models as a detuned variant for reliability and emissions.

The first major update occurred in 2006, with the LBZ boasting improvements in block and head casting the fuel system, and compression dropping from 17.5:1 to 16.8:1.

Today, the L5P Gen2 is rated at 470hp and 975lb-ft, with GM claiming the engine has proved to be capable of 550hp and 1050lb-ft.

The rods in LB7 and LLY Duramaxes are reportedly on borrowed time past 500rwhp, but later mills can handle up to 650hp depending on what they’re in. Once you fully commit, however, the big iron 6.6L can make 1500hp with upgraded pistons, rods, a girdle and oversized main studs.

PETER LIVERSIDGE
1971 HOLDEN HG KINGSWOOD

THANKS
Brian Terry (builder, mechanic, structural fabrication and engineering); NXT Level Restorations (sheet-metal fabrication, panel and paintwork); Kraken Engineering (components, fabrication, pipe work and plumbing); and especially my wife Rach – my biggest backer and supporter of all my smartest and dumbest ideas. She has made it easy to spend the time and money to make my dream come true.