6.2L Wiring Hookup??? Confused

[6600DURAMAX]

Man I am so new to this idea I dont even know where to start. It has crossed my mind for a while now to drop in a LS so I can just jump in the truck and drive. I came arcoss this Craiglist ad for new 6.2L motors that put out 425 horse or so. The guy says they are complete from the intake to coils to pan everything besides wiring and accessories. So here is the question

1. What type of wiring would I need to hook this up in my 71 ?
2. Can I use my current TH400
3. I think I would need a high pressure fuel pump instead of my Holley Blue
4. Do I need an ECM?? From what??

I have seen the MSD 6010 boxes but those are for LS motors with carbs this is fuel injected

Man so many questions