I see no reason why you can't swap it into a hot rod. GM does a pretty good job at keeping things organized, just look under the hood, so finding and transplanting the computer shouldn't be difficult. Overall, the dimensions are the same as any other small block, so it shouldn't be too difficult to adapt a mounting system for another small block. The motor mounts are different, though. The 4L60e is an electronic 700r4 so anything used to mount a 700r4 should be compatible with the 4L60. These engines have aluminum heads, but the block is still iron so the weight savings wouldn't be a huge improvement over the older small blocks.
I do agree with you, the 5.3 is an amazing engine so if you do the swap, give us details.
Have you had any piston slap yet? My dad's either 2000 or 2001 did. It's supposed to be fixed for the 2003 year. His company just traded in the truck for a new one, not because of the slap but because they trade them in at 150,000 miles, but haven't put enough miles on it to know if there is going to be a problem. After riding in the 04, I can see why people don't buy cars anymore. For less than most luxury cars, $31,000, you can get a fully loaded truck with more luxury than those cars can offer. And, you get a cargo bed. The best part about these trucks is even with 150,000 miles and a few dents from putting the truck on its side in a ditch, it's trade in value is still $14,000-$18,000.