Hi,
I have an M-21 tranny with the following numbers:
3885010, 3088330 and P7A04 on the gear case; 13846429 on the tail shaft and 3384685 on the side cover. Please let me know what I have.
Thanks,
Bob

Here is some of the info I show:

3885010=66-67 main case 1" bore
3088330=?

P7A04:
P=Muncie 4sp
7=67 model year
A=January
04=day of month

3846429= 63-65 tailshaft, 27 spline, driver side speedo

3384685=66-68 side cover with "584" stud type shift shafts

Rene
66_Malibu