This is not a full history of Pontiac V8 Heads but a help for the main 2 .. Round Port and D port..

  As more then a few people have  60's & 70's Pontiac's V8's of original guise...more then a few have had different alterations done that outwardly look still very normal for the era.

  Heads and manifolds.. ..when it comes to a bit of unknown history etc.. its needed often if orderings parts like intake gaskets.. or exhaust manifold gaskets.. hedders,  intake manifolds etc. This  alone catches a few owners & mechanics out. 

  The illustration below might help a bit but there is a HUGE amount more you can find out by researching your engine code and head code on a web search.  Here's something easy and often found of Pontiac head differences.