Non Lockup To Lockup
Geez rusty what you need is an A833 OD!!!!!
..........Which brings me to...........
I'm not terribly familiar with the development of 3 speed bells over the years. "Why can't" you modify the bell/ add a say 1/4 or 5/16 plate as a base to modify the 4 speed bolt pattern? I'm guessing you'd need to enlarge the center hole, which I did on a 340 bell AKA paid a guy with a big lathe!! (18 spline box into a 340)
THEN you could fiddle with the column linkage to shift the 4 forward gears LOL and put an extra lever to operate reverse!!!