Not that I can comment on all GMC which were made by GM but I have 3 different casting designs on my 302's. The complete one in the picture has a generator mounting bracket instead of a large 4 bolt area for mounting. I bought 6 of these once and air brake compressors were mounted on these bosses.

Most Military engines and possibly all 302's have a double rail oil pan 1/8" stiffener. These are great for making dry sump pans. I personally like the stationary & miltary blocks just for the mounting areas on both sides.

Originally the military would replace a block which needed boring. This lead to many blocks available. Later approved military engine rebuilders could sleeve a block back to 4" so a quite a few out there are sleeved. They were also required to have a standard crank. Finally that too was changed. That's one of the reasons there are undersize bearings on E-Bay in the military packages.

I purchased a few 302 statonary engines which had a large boss which made a stock style starter impossible to fit. You can just grind it off. Not sure if miltary ones had this or not.

A 3rd style has a smaller side mounting area at the front of the block on both sides.

The info from Oldcarkook is great for those begining to look.

In my opinion a 270 on the street is great engine and should not be overlooked. They are less expensive and still have the 4" stroke. Even with the small port head and a compression these make great engines. Remember that's where the "Jimmy" kraze got started. A 37 Chev cpe with a hopped up 270 was hard the beat.

Good Luck to all.


216.158 MPH 12-Port 302 GMC on 70% 171.0 MPH 302 stock head on gasoline 7 years later