Thanks guys, Ive been to ryans page before, pretty awesome stats, but most things are done by brand name not cc ect so I wasnt a hundred percent hence the questions. I was seriously looking at the 383 option because I can get a new cast crank flat tops and performance rods for this setup at $500aust (about 300US). Why wont the heads be any good for this setup, surely more compression the better. I was hoping to run about 10-10.5 to 1 compression, like I noted before detonation wont be a problem because this car has never run on petrol in the last 15years. It runs on pure LPG, I have the cash sitting ready to go just trying to work out the best options. The carb doesnt really matter for my setup because it simply acts as a throttle body for the gas. I was also told maybe changing my diff ratios might obtain what im after as well, currently cruising at 2100rpm Im doing about 65-70mile an hour.
Thanks Steve