Originally Posted by BOBCRMAN@aol.com
Basic same motor. Crank is different, flywheel, Pan, most heads are different, Blocks tend to be thin castings with very few four bolt main motors produced.
Internally, some are drilled and fitted for hydraulic roller lifters, whether they have them or not. Some just have the extra bosses. Some have no provision for mech fuel pump.
Still good for street and mild race motors, just different from the old school blocks..
I also heard the newer blocks were thinner but I've always ran the older blocks so I really don't know. I have seen a few of the newer blocks with hydraulic roller cam and also a mechanical fuel pump-but very few. For the guy who wants to run a mechanical pump it can be tough finding one of those.