Mustang Tech

Hi, new to this site, not sure if I have attached the photo correctly, but if you can see it, I am trying to identify this diff. I have a 66 Mustang with a 302, originally a six cylinder. Is this diff the 7.25 or possibly an 8”? Also, is the bolt at the bottom a drain plug? What type of oil is preferred when replacing?

That is the stock 6 cylinder diff by the looks of it. The 8inch used on the V8s does not have a removable plate on the back. It's design is very similar to the 9inch.

A regular 80W diff oil should be fine in it.
Someone may have added that bottom bolt as a drain because it doesn't look stock:

I hope they've fitted the V8 spindles (5-stud) up front and not just left the weaker ones there.

Thanks for clearing that up hybrid.

Just found another pic - I'm not sure your cover plate is stock. The stock one seems to be flat at the top and bottom to follow the shape of the housing.
Not that it matters, but maybe that is why the extra bolt is in there.

True, when I was looking for gaskets they didn’t have the bottom hole which was a bit confusing. That may explain having the filler plug & drain plug, so you don’t have to remove the plate, where on your photo it doesn’t have either.
Cheers