76 breaks problem

Dana67Dart said
If you can get under there and clean the housing and cover, there will be numbers cast into the housing somewhere.

Also details of the breather, older 7 1/4 had a cover that sticks up slightly on the axle tube (not like the vent bolt that holds the brake distribution on 8 3/4" rears.) many times they are covers in dirt and grease so not easy to see

But please put the drum on the axle flange and take a photo from the rear showing the backing plate and the drum and how they engage each other

Apologies for the delay. The car being at the shop is a pain.
So I counted and there are 9 bolts on the housing cover. I did my best with the pictures. As for numbers i couldn't find anything under there other than the tag with the numbers on the picture.