Nice! I imagine they're pretty hard to find these days, also, please edit the title so 1974 is at the end, otherwise it is very hard to find the car through a search.
I just did a quick read-up on the Roadpacer AP, by the sounds of it, pretty much everything.
However, most of the problems that applied to the car in real life have little effect on it in the game, so they could throw it in for fun as a quick duplicate of the Holden Premier with different specs and sounds. After all, I'm fairly confident that now models have reached photo-real, PD's goal is to eventually include every car in the history of the universe.
How I would make a superbad version of this truck.
1. Find an 90's Ford Ranger.
2. Pull the drivetrain and replace it with a turbocharged R20B (at least 550 HP should do nicely) hooked to a 6-speed manual.
3. Remove the body and replace it with a replica REPU body.
4. Drift that mofo.
5. Profit!