Identify Disc Brakes on Dart?

I was one of those passers!

Exactly! It's a real shame, because a whole lot of FMJ conversions got melted down and turned into Toyota's instead of providing an inexpensive BBP disk conversion for our old Mopar's. Even just 5-6 years ago there were a decent number of B/R and FMJ cars in the yards. Fortunately I didn't subscribe to Ehrenberg's theory, and I pulled a few conversions out of the yards for my cars.

At least now the 73+ spindles and brake parts are being reproduced, since they're mostly dried up in the yards, but still.