I'm partial to 351Cleveland engines, as they came with canted valves (better port angle for better flow) and oval ports (less flow restriction , as the air swirls in a round environment, gaining velocity more easily). A 2v (2 barrel heads) Cleveland is probably the best choice of clevelands. As for the year of engine, well I would say 72 is a good year (it's one i have rebuilt). They come with flat-top pistons, high compression, and a strong crank. There are a version of Australian heads available for Clevelands as an improvement to the stock 2v ones. ( this is the setup currently in my gf's 72 Mach I). I can provide you with more info on the Cleve, if you wish.

This strictly my opinion, and others will follow [img]/phpBB/images/smiles/icon_smile.gif[/img]