I just got off the phone with Darrin Grove (562-926-9552 x205) at M&H Electric and ordered a new engine harness for my 72 Riviera. The part number is 40897 ($180) for the 455 V8 with standard A/C (non-climate control). The last time I inquired about this was sometime in 2009 and I didn't have much luck. I asked Darrin for a list of other E-Body wiring harnesses that they can build and he is supposed to be emailing me so I can post it here.
Glad to hear they are making them. I know I promised you one when I parted out a Riv a long time ago, but a helper snipped it up to aid in removal! o No: