Not sure if anyone else cares as much as I do, but here's the info anyway. I swapped a 5.3 and a 6l80 into my S10 and still just have a PRND321 for a gear indicator. There's obviously aftermarket solutions for the a 6l80e gear indicator from places like speartech and dakota digital, but they were mostly single purpose and a little more than I wanted to spend. The ultra-gauge MX allows for monitoring of manufacturer specific PIDs and can program up to 8. There's not a lot of info out there on it, but I managed to piece together some information to get it working. It only shows forward moving gears and doesn't return anything (that I'm aware of) for P through N. If you're in the same boat, here's how you program the gauge.

Please reply if you know the PID for something like "commanded gear" to give more SA when using the tap up and down shifting.