Hopefully somebody will respond to Jack. I looked in the wayback machine today and I don't see anything.
The wiring for the volt and fuel gauge is consistent year to year, I would think. The wiring on the cluster was revised each time they added a new warning light, so there are probably 4 versions of it.
I don't recall if 1979, 80, and 81 are three different versions, but I think they are. The gauges themselves don't care, but you have to have the printed circuit year match the appearance-of-the-plug year. The early version is pre-seat belt warning. The mid-70's version is with the seat belt warning.
*IF* you buy a Trans Am instrument panel harness, it's totally plug and play, but it's pretty hard to install that harness.