The intercooled 1st Gen appeared as a 91.5 model. The manual trucks used a Getrag G360 transmission. It's a solid performer if you don't bomb the crap out of it. For autos, the early trucks got non-overdrive 727s. Since they had no overdrive, they got Dana 61/71 diffs with 3.07s front and rear, respectively. The overdrive trans came out around the same time as the intercooler. I'm not 100% sure of the timing, but I know it's close. There are a lot of little differences between the trucks, too. A lot of 1st Gen guys will combine parts from each to get what they say is a better product. I haven't researched those claims too much, so I have no idea if they're true. I do know that some guys will swap the ultra tall gear diffs under an intercooled truck to make a sweet highway hauler, but they obviously give up some grunt for towing.

I own a 91.5 with a G360, but its drivetrain is going into my 78 crew cab. I also own a very early 98.5 24V, and it's been a super reliable truck. As mentioned, the lift pumps suck, so they need attention.