Editing 3959088

Might have a chevelle rearend i just purchased for my gto.  On the differential i have 3959088, GM5 and 1924.  I haven't noticed any numbers on the axle tubes possibly because of rust?  I think it is out of a 68 or 69 chevelle but really don't know.  I would greatly appreciate any insight on these numbers!  thanks matt b.