Where to buy drum brakes kit

Hmm.. I’m not sure *at all* if there are any nuanced differences between B or E body rear drum brakes versus A body. If you do go that route... I would measure and double measure the shoe sizes and drum width ( just to make sure what arrives in the mail is the exact same dimensions as what you take off).

Are your rear 11” drums not OEM for your vehicle?

Also, if you look up 1975 dart sport with 225 size engine... there is an option for 11” drum (for the front though; not the rear).