Thanks for the replies, it's a nice restoration on the car but there was no info from the previous owner so it requires a bit more investigative work. The M20 is a 1970 year.
I couldn't find that serial code yet, just using my phone's camera with the car not jacked up isn't ideal for...
I've been planning for an engine upgrade from a pretty clapped out 350 in my 1973 camaro LT split bumper. It has a Muncie M20 4 speed manual with code P0827A signifying that it's not a numbers matching part, and with the rear diff it's a 10 bolt that I can't seem to find enough numbers on. Maybe...