Alright after doing a lot of research I've decided that the .484 MP cam is really the biggest that should be put in a 383. I'm thinking the .474 grind MP cam is a good choice with my 4 speed and 3.23 gearing. It should also work with my factory AC, even if I have to swap out the factory pump for an R134 pump. I will also shave the heads and port'em to get better flow and CR. IMO, from what I've been reading, my 346 open chamber heads can perform just as good as a closed chamber head once they're built right.