We butchered up a lot of floorboards back in the 60's installing floor shifters. Just about any shifter can be adapted to your trans, it's just a matter of getting the shift rods and the bellcranks positioned right, plus bracketing the shifter to the tailshaft of the transmission. Get a big hammer, a hacksaw, a torch, a welder, and a pile of scrap steel and make it work. It will be butt-ugly and unreliable, but that's exactly what we ended up with back when we were know-it-all teenagers!
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!