dimensionally, the 350 heads are pretty much the same throughout the entire 1968-81 production run. Buick controlled static CR ratio with the piston dish and pin height. if you want the 315 gross HP rating of the 1970 'SP' code engine, you'll probably just want to step up to new light weight pistons and NASCAR takeout rods.
be aware that 72 was the first model year of "SAE Net HP" ratings, and these are significantly lower than Gross HP numbers due to testing methodology. 1971 and 72 engine packages were very similar but the highest rated 1972 350ci engine was only 190hp Net, while the 1971 engines were 260hp Gross.
largest difference is that the 1960s Buick small blocks oiled the rockers by weeping from the rocker shaft while newer engines use the 'Chevy style' pushrod oiling via hollow pushrods. i think 1970 has pushrod oiling, but i'm not certain. old heads on a newer engine will work fine, but be certain that there aren't any old style oil ports in the engine deck that need to be blocked off.
the early heads are supposed to be thinner castings and more prone cracking.
you can drop in an HEI distributor from a later Buick engine, although you'd need to swap the gear at the bottom of the shaft if you pull the HEI out of a 455. you can also take an 800cfm Quadrajet off of a late 70s engine. Buick designs tend to like more carb.
we host the 2006 Jim Burek head porting article here and we have other 350 specific performance articles under the "Reference" button at the top of the page:
https://www.teambuick.com/forums/con...orting-article
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