I am in the middle of doing this very swap on my '74. A buddy of mine is upgrading to an LS in his '87, so I decided to run his old TBI stuff vs. going LS. I found a lot of good tech here:
http://www.binderplanet.com/forums/f...splay.php?f=75 , and here:
http://67-72chevytrucks.com/vboard/s...d.php?t=352321 .
I used the wiring harness from fuel injection connection. It is all new, and was relatively inexpensive, at $245. It is labeled, and it is a really nice harness. Robert has answered any questions I have had pretty quickly, too. Their site is
www.fuelinjectionconnection.com . I also had teh luxury of having an '87 parts truck, but the engine, trans, ecm, and harness were long gone. I pulled the fuel tank, but with TBI you could probably either run an external pump, or just buy a new tank & sending unit. The lines in my parts truck weren't all that great, so it wasn't much of a bonus there. You can get most of what you need from a 87-up Suburban or Blazer, too. Not sure about your area, but they are fairly plentiful in the pick a parts here.
The binderplanet site is pretty cool in that a lot of teh guys there are adapting the GM TBI for use on their existing IH engines. Compared to that, we have it easy. I feel like I wussed out buying a new harness compared to those guys....