All 327s were 2-bolt mains, West, and the '67s and back had steel cranks. In '68 they went to the larger main bearings, the block lost the canister oil filter in favor of a spin-on type, and the cranks were cast. In general, the older 327/210hp version was a 2-barrel, the 250hp was a 4-barrel with a 4GC Rochester, and the 275/300hp had the 1.94/1.50 heads, more compression and a Holley carburetor. That's just the base 327s. One sure-fire way to identify a '67 and back engine is that they had a breather tube in the back of the block beside the distributor instead of a PCV valve, and they had the steel canister oil filter. Hope this helps.