ID a old rear end/ differential

Can anyone tell me what size these are just from the pictures. It’s a 79 Freightliner with aluminum frame

 

I lost my password to my account, I just made this one. If it’s in the wrong forum just let me know and I’ll repost elsewhere

 

Ok thanks, I could make out a few stamps on the housing. 3776 but wasn’t sure what it means, I’ll be picking it up Monday.

 

I was hoping that they weren’t 38,s I know they were pretty common back then

 

Not a bad looking old truck for the price

 

Thanks a lot man

 

4000$ 400 big cam 2, 13spd, and decent tires all around. Gonna buy it and run it. Figured it worth that for scrap price since it aluminum frame and good drivetrain