There have been a couple that have done the swap that I know of. Two of em have just cut the front of the frames off and swapped em. Theres a thread in the pics forum on here. As far as difficulty I wouldnt know since I havent done it haha
It's def possible, but no where close to a bolt in option. You need diff motor mounts, different converter, custom headers, swap in wiring harness, pcm, etc.
If you're thinking it would be an easy cheap way to get 380 hp out of your Gen 1, think again. It costs a little more to get a Gen 1 into the 12's than a Gen 2 (although the cost of the truck is more Gen 2 wise), but it's cheaper to get a Gen 1 into the low 11's to high 10's than a Gen 2. Once you get past that, they're all expensive lol.