What does the shape of the pan look like? A 400 has an odd-looking kidney-shaped pan with a bulge about 2" wide on the passenger's side. Other GM transmissions like the TH 350 and 700R4 have rectangular pans. The 350 has one corner of the pan lopped off at about a 45 degree angle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!