Personally, I'd suggest a 94-98 2500 with the 12-Valve Cummins diesel, the 96-98's have a little more power and upgraded interiors than the 94-95's. The Cummins is damn near bullet proof, gets incredible fuel mileage, is easy to maintain, and even easier to modify for more power. The 98.5+ 24-Valve Cummins have computers and a different fuel system, which to me is too much foo-foo to deal with, since the 12-Valve requires 1 wire to run and has proven itself reliable.
The 2nd gen gas trucks had 5.2 and 5.9 Magnums in 1/2 tons, and the 5.9 Magnum, V10, and Cummins Diesels in the 2500/3500's. The 5.7 Hemi didn't come out til 3rd gen.
Automatic transmissions are junk, no matter what engine is in front of them. Fortunately, they are easy to beef up, but that can cost some dough. The manual transmissions are better, but still have their minor issues. The 1/2-ton rear differentials are weak, the 2500/3500's got beefier Dana 70 & Dana 80 rear axles.
I don't know anything about the front axles in the 4x4 trucks, but I know the 2500/3500's have alot of slop in the steering due to a weak frame at the gearbox mount. There's a cheap fix for that though, not sure if it also applies to the 1/2-tons. I'm sure someone will chime in with more specifics.
I've owned two 2nd gen 12-Valve diesels, one was a 2500 Automatic, the other a 3500 Dually 5-spd Manual, both 2wd, so I don't have personal experience with 4x4 Dodges, but I've got a few friends with 2nd gen 4x4 1/2-tons, all of which have had major problems with engines, transmissions, and front/rear axles with under 200k miles.
My old '97 Dually got 26mpg on the highway, while a friend's '98 1/2-ton 4x4 got 12mpg with the 5.9 Magnum. Another friend had a '98 2500 Club Cab shortbed 4x4 with the V10 and he got around 10mpg with it. I'll gladly pay $.50 more per gallon for diesel if it means I'm getting double the fuel mileage of a gasoline counterpart with a Cummins.
This is just personal experience, and personal opionions talking...