"Chevy" 307 vs 305 or 350?

Ah, but that's how conversations go. To the OP: I've always wondered if Olds 350 heads could be bolted to a 260 or 307 block with no modifications, and if there is a ready-made intake that would match the 350 intake runners without major modifications? Or, conversely, itf the 307 heads have enough metal to allow the installation of 1.94/1.60 valves without intruding into the water passages?

 

They do. All Olds heads have sufficient material to install the 2.070/1.625 big block valves. The 260 heads and the 7A heads used on the roller cam 307s have worthless peanut ports that negate any attempt to increase airflow, however. Also, small block Olds heads were cast with chambers that vary from 64cc (early 330 and 350 heads) to 80cc (smog heads). Coupled with variations in piston dish sizes (from flattops on W-31s to soup bowls on some smog motors), you can get anywhere from 10.5:1 to less than 8:1 CR.

 

Yeah, that makes a whole lot of sense. I just have never researched Olds engines beyond the '71 350 I had a long, long time ago.