Well all of the M112's and M113's bolt up lol. The exhaust manifold fab can be overwhelming, I sell sets. The AC compressor mounting can be annoying. The wiring is the biggest nightmare you'll deal with other than ECU work if you tried. Flywheel and clutch will depend on what year motor you buy. The 4.3's and 5.0's are the best IMO because they have so much potential compared to the 5.4 NA. Obviously the 55K is the way to go, but good luck lol. From an NA, that's going to be a huge job, and I haven't quite got the electronics to work for a manual yet. Like everyone said, do your research, come to me with a game plan, and I'll let you know if it's a good idea or if you need to find something else, or add more to your list.