Most of the guys on full size jeep board look at the 20 and 44 as being virtually equal in strength (and yes I've got my asbestos skivies on). The full size rigs with the 20 (called a 23 in those) have a flanged shaft. Was me, I'd keep the 20 and put either a flanged shaft kit in it or a full float kit with locking hubs (makes flat towing a breeze).
I've got a 20/23 in my big 81 cherokee with a 360/T18/208 in front of it with 3.31's and 31-10.5's. Not a problem, and I don't cut it much slack at times. Only broke one shaft and that was on pavement, had been cracked a long time when we got it out and looked at it.
1981 Cherokee W/T, 360, T-18, Warn 8274 in custom bumper/deer strainer (tested and approved)
1988 Cherokee 4 door, 3" Rancho lift, custom sliders/steps, custom roof rack, custom camo paint, custom camo headliner, custom bumpers and Warn 9500 HS, 31-10.50's
Only 31's, but can drag self with either rig
BLM John Day/Snake RAC-OHV Representative
Wolfpack 4x4's - Region 5 - "Cave Lupum"
VP- Outcast Land Use Review Team