I put the 87 TBI in my '74. I used a harness from
www.fuelinjectionconnection.com. Robert was really great to work with, and the harness was really reasonably priced, too ($245 shipped). I mainly did it so I wouldn't have to deal with 25 year old wiring. His harness deletes emissions, so that really didn't hurt my feelings either. You use teh original ECM, though. For fuel, all you have to do is run a fuel feed and return line, and mount an electric fuel pump. I was able to use a factory '87 tank in my truck, but using an 87-91 Sub/Blazer tank would work for you, and you could use an in tank pump. If you are using a 700R4, I think you could adapt a newer brake switch and use the TCC, (that's what I did), and I used a VSS from Jags that Run ($75) so I could run my original cluster. It goes on the transmission, between it and the speedo cable. If you have a running donor, that would make things a lot easier.