Re: 84 CJ/Scout T19/D20/D44\'s
If the motor is strong and the tires aren't bald, I'd do it. The t-19 is the Scout version of the t-18...good strong cast iron tranny. The Dana 20 is also strong, cast iron, all gears t-case. Not much to go wrong with either and both wil take ALOT of abuse. The D20s only downfall is the crappy low range of 2.03:1, but if t-19 has the 6.31:1 low range and with the 4:88 cogs I wouldn't worry about the Dana 20...you'll have plenty of crawling ability (62:1 crawl ratio). The Dana 44s are pretty stout too. The spool is almost indestructable.
The axle setup is the same as mine assuming its SUA (i.e. springs outboard the frame). I don't have any complaints about mine at all. The Scout caster is zero degrees versus the CJ caster of anywhere from 3-6 degrees, but that has not been a problem for me. The steering just doesn't return to center as fast as it did before.
To build up your YJ to that solid of a drivetrain (d44 axles, t-19, gear swap, spool, locker, 36x12.50s) would easily cost you a few thousand on the cheap, more if your not doing all the work yourself.
I'd want to know the answers to the following:
Why is the guy selling? Who set up the gears? How long ago? Any gear whine at high speed? What brand gears? Who outboarded the d44? Was the t-19 overhauled before install? Was a new clutch disk, throwout bearing, pressure plate used? What brand? Any receipts (for the locker, spool, clutch, etc).
If the jeep is in the condition you say, I would pay $5000 for it.
Just my $.02.
77 CJ7, D44s, Detroits, 4:27s, 35 SSRs, HS9500i
84 CJ8, 33s, REP8000