On the PROM, I had mine reburned by Brian at tpichips.com. I told him what I had for a motor, what I had deleted from the factory harness, and he did the rest.
On the harness, I bought the factory Helm manual for the car and rebuilt the factory harness. I can tell you that it took me MANY nights to do it, but I learned a TON about how the whole system worked. I would highly recommend buying the Helm manual and using the factory harness.
I bought my fuel tank from boardmember fuelcellguy. He set it up with an intank fuel pump that was all setup to work with the TPI.
Other useful links:
www.jagsthatrun.com - they have a great TPI book, and I bought my VSS and air ducting from them. Their book helped a little with the wiring harness cleanup too.
www.chevythunder.com - great resource. Also helped with the wiring harness cleanup.