Rear end identification

[renegade8720]

Hi, the 50 Chevy truck I just purchased has a later model rearend under it.
How do I ID this rearend to tell me what it came out of and the ratio? The only numbers I have found so far on the rearend on the back side of it on the axil housing is 87890. On the front side next to the yoke are the numbers GM57 on one side and 3917123NF with the letter X above it.

Thanks for any help,
Renegade

[rstrick]

There is some information here about your casting number:

http://myweb.cableone.net/mdthode/67...tial_Codes.htm

and here:

http://www.chevellestuff.com/qd/gene..._axle_info.htm

Looks like it is probably a 68 Chevelle 10 bolt.

[renegade8720]

Thanks for your help!

Renegade