I got a 72 model, I think, 500 engine with 902 smog heads. I'm still learning about these engines but I know basic principles carry from any V8 to another. First, the 902's are 76cc I believe closed chamber. Is that head worth messing with or would a 120cc open chamber head from another year 500 make more sense for a big torque 4x4 truck motor? Second, if I use the 902 heads, I was going to install larger valves and unshroud them and do some mild porting and polishing and gasket matching. I would like to, ideally, weld or somehow block, from the exhaust port side, the heat crossover and emissions holes next to each valve guide. Can this be done, is it worthwhile, can I even weld to the heads? I don't know whether to go big open chambers and a dome piston setup for more flow or keep the small chambers and flat tops to keep CR around 9ish. What is the advice of the wise ones?