Saginaw 4 speeds have a very rugged cast iron case- - - -you probably don't need a rear crossmember unless you just want it to be there for some reason. Even the aluminum case Muncie 4 speeds worked OK without a rear mount on some applications.
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!