As long as the transmission isn't overfilled with oil, and/or the vehicle isn't parked on an extreme downhill angle, there won't be any leakage into the bell housing. Later transmissions such as the Saginaw 3 and 4 speeds did have a front seal, but the SM 318, 319 3 speeds, and most SM420 4 speeds didn't have one.
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!