oh, and I forgot to completely answer the other part of the question...3 speed tranny cover is completely flat, with a few horizontal stamps. Hydramatic tranny cover is essentially the same, excepting a hole where the transmission fluid dip stick fits. 4 speed has the hump.


1956 GMC 100 NAPCO Deluxe
1955.1 Chevy 3600 NAPCO
1954 Chevy 3600 NAPCO