gm/chev differential casting numbers
 

hey there, I know there are a thousand and one postings about casting numbers, and I've sifted through a bunch and have not had luck finding exactly what I'm looking for... any help is appreciated .. especially from anyone who has the book 'Chevrolet by the Numbers'

so, I started cleaning off my diffs and changing their fluids etc... My 64 chev stepside is a basket case of mixed and matched parts from what I can tell .. the cab vin says its a 2wd 66 suburban, the frame says its made in 63 and I have four wheel drive, with a closed knuckle front end, factory correct looking hubs, factory correct looking transfer case...


anyway, I'd like to identify for certain the actual type of diffs they are ..

rear diff raised lettering near filler hole: 3817778M

front diff raised lettering: C31256 44 5F

again, any help is appreciated! :metal: