i have three of numbers on right side 385784GM on cover also 3858403 and 5851325 on is on tail shaft

3857584 is the '65-'69 Muncie tail housing
3851325 is the '64-'65 Muncie case
3858403 is a '64-'67 bell housing for Pass. (283. 327
usually w/10.4" exc. HD Clutch)

where did you find that information ? cause i looked , and where do i find the code that tells which muncie i have. one other ? how do I figyre out if car was actually put together in 65 or 66 cause the assemble date is real close to my birthday but the motor seems to be a month older than the car

http://www.5speeds.com/muncie2.htm

this tranny has an aluminum case does that mean it is a rock crusher or did other muncies have the same case

All muncies had aluminum cases.