That's possible, but the problem I can see is that Bolwell isn't really known for much (I'll be honest, I had never heard of them before this) and I can also see a problem in that the Bolwell cars were all powered by cheap, tough Ford V8s. A Repco V8 wouldn't work so well for this application, as it would cost more for roughly equal power and performance (lighter weight, but less torque) and have an engine which would likely be more finicky.
If you wanted to go this route, have Repco develop a V12 version of the Repco V8 using the same cylinder bores and head designs. The F1 versions of the Repco V8s made roughly 375 hp, so tune that down to say 280 hp or so, plus the addition four cylinders, you get a roughly 400 hp engine, which in the chassis of a restyled Nagari could be genuinely interesting, particularly if they go racing with it. Even if the company just runs Le Mans in, say, 1971, they could get a rep. Le Mans' GT category in 1971 was made up of two Corvette Stringrays, a Ferrari Daytona (which won the class) and a bag of Porsche 911s. The Nagari was a featherweight compared to the Daytona or Corvette Stingray and had at least twice the horsepower of the 911s, so if it gets home, powered by its Repco V12, would be a huge win. Australian drivers didn't get a lot of respect in Europe at the time - when Peter Brock and Larry Perkins took on Le Mans in the mid-1980s, they were seen as backup to the ringers - and an all-Aussie team, with an Australian supercar with an Australian V12 engine and a bunch of Australian drivers, winning the class at Le Mans could stun stupid many of the people there.
On top of that, after the five-liter Porsche 917s and Ferrari 512s are out after 1971, in could come the Repco engine as a rival to the Alfa Romeo V8s and Porsche Flat-8s and Cosworth DFVs as an endurance engine. Build a reputation for being capable racers at Le Mans, which would then get you interest in North America (turbocharged Repco V12 in a Can-Am car, anyone?
) and Europe, and you build great road cars to go with it.
Thinking far ahead, maybe Holden decides to use the Repco V8 to counter the Cosworth V8 in international racing, and so the Holden Repco returns to F1 in 1973 or 1974, perhaps with McLaren. A good showing by the Holden-supported Repco V8 powers James Hunt to his famous championship over Niki Lauda in 1976, while a Bolwell GT car gets into Aussie touring car racing, and thanks to Christine Gibson (I had to
) the Bolwell conquers the Holden Toranas and Ford Falcons in mid-70s Australian touring car racing. By 1980, Bolwell is Australia's producer of great GT cars and fearsome racing cars and Holden (and thus GM) is only too happy to back them up, knowing that abroad they can, and do, kick a lot of ass.