I have a Muncie M20 for sale. I believe it to be from a 70 Pontiac (bought off of CL, so I can't really be sure). It has been completely dissasembled, cleaned, media blasted, and clear coated (2 coats) and reassembled. Has new gaskets and seals. It appears to be in perfect condition. No cracked or chipped teeth. The CL listing said that it had new bearings, and I believe it. The input shaft is as tight as I have ever seen, with only about 1mm play. The case (660) has no cracked or broken ears or welding done on it. It also has a drain plug. All threads have been chased and there are no helicoils. Shifts smoothly and crisply in to all gears. I was going to use this tranny in my 66 442 project but decided to go with a more correct M21 with the 3.90 gears I got for it. $700 plus the ride. Please send me a PM if you are interested.
Thanks,
Randy

 

Here's a couple more pics..........

 

Main case was: P0K25B

P = Muncie
0 = 1970 model year
K25 = July 25, 69 assembly date
B = M21

&

40H115479

4 = Buick
0 = 1970 model year
115479 = VIN sequence of original car it was installed in

 

Thanks for the decode. It really is an M20 now.........