Upload a picture of your transmission pan and the sides of the transmission body. Most common would be a C6 or a FMX I reckon. But it could have been swapped out for something like a C4 sometime in the last 50+ years.
You can use the door tag or marty report to tell you what transmission was originally in your car. That doesn't mean thats whats still there.
Mine was painted over, too. I got a new one from Marti, as well as a Deluxe Report. The Deluxe Report will tell you what engine, transmission, rear end, paint color, interior, etc that your car came with.
It does appear that it is an FMX. One sure way to identify an FMX is that it will have a cast iron body, with a bolt on aluminum bellhousing and aluminum tailshaft. All others have aluminum bodies. https://www.martiauto.com/martireports.cfm
C4 - 3 pieces, all aluminum bellhousing, main case and tail shaft.
C6 - 2 pieces, all aluminum - main case and tail shaft (CJ and PI use iron tail)
FMX - 3 pieces - aluminum bell and tailhousing, iron maincase.
If there are four bolts holding the main housing to the bell housing—it’s an FMX. It can be pulled similar to a 4-speed by taking the four bolts out and leaving the bell house connected to the engine.