I searched around for another aftermarket kit and found BAER Brakes with beefy kits from 11 to 14 inch rotors !
They advertise them as B/E-Body Mopar compatible but do list 73-76 Darts "OE disc spindle" compatible. So, I've reached them and asked to clarify if I need a B/E Spindle or keep my 74 OE Spindles...
Mark Fowler BAER Tech Support/Sales said
The system in question (Baer SS4+ Front kit) fits the OE 73-76 Dart disc brake spindle which is similar to the 73-up larger B-Body spindle.
