Aussies have long loved an HQ, but we’re finally seeing a greater appreciation for the other large-bodied 70s Holdens that came after it. And when you look at a car like Andrew Broadhead’s 1976 HJ GTS, it’s easy to see why.

First published in the February 2026 issue of Street Machine

Originally featured in SM back in June 2020, Andrew’s genuine GTS Monaro has been treated to a complete rebuild into this stunning brute, unveiled at Street Machine Summernats 37. Previously a tidy streeter with a 700rwhp LSA, it’s now sporting a 1225hp Harrop 2650-blown 427ci LS, radiused tubs and four-link from ProFlo Performance, a fresh Down Town Kustoms custom metallic brown paintjob and millimetre-perfect body, and a cutting-edge interior with 3D-printed parts.

“This all started one arvo in late 2020 when we were cruising with the kids and heard a rather loud suspension knock in the right rear,” Andrew explains. “Once home, I investigated and found the brake bleed nipple was hitting the rail to the point it was almost gone. The diff housing was way too short, so some calls were made.”

Andrew hit the Yellow Pages and gave ProFlo Performance a call to book the HJ in for a new rear end. In addition to pushing the radius-edge mini-tubs to the chassis rail, Paul Sant and his ProFlo team installed one of their four-link set-ups and a sheet-metal nine-inch diff packed with a Strange centre, Truetrac LSD and 35-spline axles, along with a new boot floor to cover the lot.

With the rear end now sorted, the bodywork came in for attention. The more-door Monaro had previously been painted a custom dark candy purple, and Andrew initially planned to simply paint the new parts to match and get a new rear seat made – until he got in touch with Graeme Brewer from Down Town Kustoms. “I got talking to Graeme about refreshing a few defects in the paint, and that is where it all just snowballed.”

A scant week after the car arrived at DTK, it had been stripped to bare metal so Andrew and the Down Town crew knew what they’d be up against. Although it was a clean streeter tidy enough to score a feature in this very magazine, there were issues hiding beneath the surface.

“It could have been worse, but it wasn’t pretty,” Andrew says. “There was lots of rust, and lots of ‘old school’ repairs. It was disappointing, as it seemed like a sound body. So, the quick paintjob turned into a far longer and larger project, with even more fab work, tidying of bodylines, and sharpening everything up.”

This massively undersells the amount of work that took place. It’s an exhaustive list that includes tucking the bumpers; extending the beaver panel for a clean flow into the rear bar; shaving the fuel filler; shaving and metal-finishing the body seams; deleting the rear door vents, raising the floor to accommodate engine and transmission oil coolers; sheeting out the boot and rear firewall; shaving and smoothing the engine bay; adding a custom plenum to hide the reversed BA Falcon wiper motor; and fabbing a matching custom radiator cover to make the intercooler pump, catch can, wiper bottle and radiator disappear.

Once the body was slicked and sharpened to perfection, a custom PPG metallic brown was mixed by the DTK crew and expertly applied. But now the HJ looked too good for its old engine.

“I couldn’t really just throw the old LSA back into it, so Paul got another call and a request for a neat 427 Dart LS,” Andrew explains. “The brief was simple: something capable of 1000rwhp that behaved on the street.”

A Callies Magnum crank and Ultra rods live with Diamond pistons to create a rock-solid foundation for boost, with a custom hydraulic-roller cam, high-volume oil pump and gated Moroso oil pan rounding out the bottom end. Top-shelf Mast Motorsports Black Label six-bolt heads have been fitted with Texas Speed rockers, topped by a ported Harrop TVS2650 blower pushing a tonne of boost, which caused some teething issues.

“When it went 1225hp on the engine dyno, we were rather happy,” says Andrew. “But on the hub dyno, there was a hell of a lot of belt-slip, with the boost dropping to single-digit figures at the top of the pull, and this resulted in a somewhat embarrassing 500-odd horsepower at the hubs. Now it’s fitted with the new Harrop tensioner, a shorter belt and a Griptec pulley to hopefully alleviate any further slip when we get around to getting it back on there. I’m sure with the new pulley and tensioner, it will make for a fun drive.”

The blown LS is backed by a manualised, forward-pattern TH400, which gave Andrew some trouble in the lead-up to the car’s unveiling at Street Machine Summernats 37.

“In true Summernats form, during final checks prior to tuning the car just before the event, the transmission shit the bed and started pissing fluid out the vent,” Andrew sighs. “Rob Godfrey and I had to rip it out, go and get a new pump put in, dyno the transmission, and reassemble the car just a few days shy of the ’Nats – good times! Then Rob and I did the most hilarious wheel alignment in the shed on 29 December, and the interior didn’t even go in the thing fully until the following day. Mick Carter was stuck between this and Frank Zammit’s ENDLESS XW ute (SM, Apr ’25), with both the ute and the HJ having exactly the same leather, but he really did a great job and we are very appreciative that he donated his holiday time between Christmas and New Year’s, even when he has such a young family.”

Thankfully, the car made it to the ’Nats, where the covers were whipped off the delicious Monaro to a rapturous reception. The HJ also found favour with the judges, snaring Runner-Up Top Pro Sedan, before backing that up with third place in Street Elite Top Interior at Meguiar’s MotorEx 2025.

Despite the car finishing up far, far nicer than they’d intended when Andrew bought it six years ago, the HJ is now destined for a life of cruising with the family. “My wife isn’t particularly keen about it being driven, but this is why we built it, so we’ll cruise it cautiously for now,” he chuckles.

ANDREW BROADHEAD
1976 HOLDEN HJ GTS MONARO

THANKS
Graeme, Damo and the team at DTK; Paul and his team at ProFlo; Mick Carter for all the trim work; Jared at Concourse Moulding Repairs & Polishing; Rob Godfrey; Adam Povey; Jamie Galea; last but definitely not least, Raelene and both my boys for putting up with the late nights and the years putting this thing together.