A Saginaw case is considerably longer, and the side cover has 7 bolts instead of 4. It also has a synchronized 1st. gear. The Saginaw 4 speed uses a very similar case shape, and Reverse is moved to a different shaped rear housing to make room for the 4th. forward speed in the main box. Borg-Warner did something similar back in the 1950's with their T-85 heavy duty 3 speed and the T-10 4 speed.
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!