:confused: I don't know much about gearing, except that I need to regear. I have a 1980 GMC Sierra, I just rebuilt the 350 4-bolt, RV cam .30 over, flat top pistons, and an Edelbrock 600 carb. From what the rpo code tells me it has a 3.08 ratio and this doesn't do very well with the 35x12.5...