The Mighty 396...NOT!

Oldsmobile 402.
I think pontiac had a 403
Probably just to differentiate between brands, ie they didnt want to call it a 400 becasue there was a small block 400. And the 396 was already a popular motor. Whats a few inches? Ford had 3 351's and a 352 as well as a 427. 428 and a 429....and then their Are all the sibling hemis....