It is not just from flywheel to wheels. It is also due to intake restriction, headers that fit a chassis rather than being dyno fixtures, alternator, PS, water pump, exhaust system.
Do a search and the above referenced Fleetwood guy has I think a 440hp package that put like 325 to the wheels. I am not trying to knock Golen just trying to help you understand the realities involved. You want more power order a MUCH higher rated package.