My 1968 GTO has a 1972 WM code 455 cu.in block. All my research indicated this should have 4 bolt mains.and came from a 1972 Trans-Am. I am in the processreplacing the rear seal, and when I removed the pan was surprised to see 2 bolt mains any answers to this question would be appreciated. Dan

 

What is the actual casting code? That'll tell you for sure what's supposed to be under there.

http://www.pontiacpower.net/engcode01.html

 

Dan68 Your unit # at the back top of your block near dissy numbers,485428 are Ram air 4 bolt mains, The #s wont lie, See if you can find them 485428. Good luck.