An SM 318 would have been the original 3 speed, but you'd need all the column shift linkage to make it work properly. A floor shift conversion would put you in the same situation as the Saginaw 4 speed.

There are dozens of Saginaw 4 speed shifters available on ebay- - - -mid-1970's Vega cars ran them, along with Oldsmobile and Pontiac pony cars of similar vintage. I mentioned this the last time you brought the subject up, also, and even found the Ebay listings for you. This time it's your turn to search.
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!