I got a really good deal on a 350 out of an 87 chevy van. Only $100 running . So anyway, I want to rebuild the engine but I was thinking about using my stock 305 heads temporarily until I can get a better set. What do you think the CR will be with the 58cc heads? I don't want to run anything crazy.

 

That's a pretty good idea, actually. However, some porting work on the 305 heads and 1.94" intake valves would be a good idea to help the 350 breathe like it should.

Unless the bottom end absolutely needs the rebuild, it would be best to keep the factory dished pistons with that combo. That'll give you a mid-9:1 CR. Most 350 heads are 64cc or 76cc, though, so if you build the bottom end with the end product in view (64cc heads with flat top pistons is the "good" combo), flat tops with 58cc heads would still only yield about 10:1. Extra thick head gaskets would help to lower it a little until you got 64cc heads on it.