I can tell ya here!
It is a 1968 tranny, but it would depend on how many rings are on the input shaft to whether it is an M20, M21, or M22.
26- April 26th
W-Willow Run assembly plant...not sure what was built here in '68, maybe Novas.
336031-VIN from the car it came from.
Rings on the input shaft indicate what the transmission is...
No rings- Possibly an M22 if the gearset is original. M22's will also have a drainplug in the case.
1 ring-M21 close ratio
2 rings-M20 wide ratio