From what I have seen the Y block seems to be one of the most cobbled togather motors after they leave the factory,I heard stories of them having many different years of parts including mismatched heads.  I went to look at a cheap 57 292 tonight for a set of heads for the 62 292 I will be building and it had a set of 60 heads which have the same sized valves as the 62 so I am still looking,along with the newer heads it had two styles of exhaust manifolds and a 56 on back 2 bbl intake.

Butchering up everything I can get my hands on in Dayton Ohio