Murray won pro-production turbo with their usual race car and Unlimited with the X3.
Cognito won UTV overall and pro-production NA.
Most factory sponsored racers are running a full tube chassis one off purpose built race car that is basically nothing like a factory ride minus the name on the side, the motor and transmission. Heck a bunch of the 2 seat cars you see racing started life as a 4 seat vehicle. The rules are very liberal in that sense, i think all you have to keep is like the 2 bottom main tubes of the factory frame and the suspension mounting points have to be same measurement and distance "identical" to factory. Dont quote me on that but it is something similar to it. The rules make you change things like fuel tank and firewall construction making these cars very different from the factory, doesn't matter what factory either Popo, Can-Am, AC, John Deer
There are a lot of build threads on here you can search through to find the differences, The RedLands car would be a good one to look at...i think one was posted recently by Madigan Motorsports. You could also look at the thread of Joey and Cagewrx car being built right now by Cognito, it is a XPT.
Shoe string budget racers might have more fun mixing it up at the local or regional races then taking on the factory backed BITD guys. Win some local races and get sponsored by a local shop then move up from there.