This is actually written for the Toyota Land Cruiser, but since
extensive use is made in existing JEEP Swaps of GM trannies I think
(since everyone here has been so patient) you will find this relevant:

"21.2 Diesel Engine Swaps
I'm starting here because to me this is the swap that makes the most
sense for a rock-crawling machine and is probably the least explored.
As you'll figure out shortly, I'm pretty opinionated on this one and I
welcome anyone to dispute my views. __I believe that diesel engines
are superior to gas ones for offroad use__ (emphasis mine-but a common
view in ROW) for many reasons. They tend to make usable torque at
much lower engine speed than gas engines. This means you don't need
nearly as low a crawl gear. They also feature a much flatter torque
curve. There is no ignition system to fail because of moisture. They
are not as affected by altitude, in fact, turbocharged diesels are
virtually immune to altitude. In most cases, even though they have all
the advantages of a fuel injected engine, such as the ability to run
at extreme angles, they rely on mechanical injection which is
considerably simpler than electonic injection. Diesel engines also
tend to get much better fuel economy and greater cruising range than
gas engines of similar displacement.

There are three commonly available engines that are suitable for
swapping into Land Cruisers. Probably the biggest obstacle to the
conversion is finding the engine itself. The GM engines are the only
ones listed here that are available in light-duty automotive
applications. The others are all industrial/medium duty truck engines.
These motors tend to be snapped up as soon as the vehicle they were in
is wrecked and rebuilt by companies with exclusive licenses. Unless
you're willing to pay top dollar for a rebuilt unit (not a bad idea)
you have to somehow find a way to intercept a motor before the
rebuilders get their hands on it.

The most easily obtained is the GM 6.2l diesel. A conversion kit is
available from Mark's Adapters in Australia to mate a GM diesel to a
Land Cruiser 4 speed manual or automatic transmission. The GM V8
supposedly weighs about as much as a big block, so pretty close to the
weight of a 2F. The L65 is found in C/K 2500HD trucks, C/K 3500 trucks
and C/K 2500 Suburbans. The L56 is found in C/K 1500 trucks. C/K 2500
LD Trucks, K1500 Blazers/Tahoes/Yukons, and C/K 1500 Suburbans. The
6.2l is found in all pickups and Suburbans, and in Chev/GMC P30/P3500
step vans."


From the same author: later

"There are only a couple of reasons for putting a motor bigger than a
383 or even building a high horsepower 350. They are if you intend to
put on tires that are so large that re-gearing to return the tire:gear
ratio to something approaching a stock level is impossible, if you
drive your truck in deep mud, snow, or sand, or if you never quite
managed to get that adolescent desire to try to peel your tires off
your rims out of your system. "

(I always had to buy my own tires and so never had any desire to burn
rubber. That's for punks.)