Re: D20 Tcase from Scout?
Internals and case are pretty much the same. The only difference is the front output shaft, it uses the same yoke but a different size bearing. Also the front bearing retainer is different for the shifters. I think you can use the Currie twin-stick for the Jeep Dana 300 on the Scout Dana 20, or do some slight modification to the shift rails to use Dana 18 levers, which I did.
1978 CJ-5 258 Weber, 'glass body, 6.32 low Ford/Scout T-19, 2.46 low Scout/Ford/Jeep Dana 20