When swapping bell housings find someone with a dial indicator and check that the pilot bearing is concentric with the bearing retainer hole in the bell housing. If it's not concentric the transmission's clutch gear bearing and its pocket bearing won't last long. I have read that some of the bell housings were way off and that offset dowel pins were once available. Perhaps the Novak Jeep people in Logan Utah can help out here if needs be or the Pirate 4x4 people. Both have good web sites. I believe one of those is where I read about the concentricity issue. I checked mine last time the transmission was out and it was out of concentric to 0.010. I put it together anyway. I'll be dead before it wears out.

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.