10" rear drums on 69 Dart

Don't believe everything you read. RA (and a lot of others, too) are full of hooey with some of their listings. They even list '66 Darts with 383s- no such animal ever existed (from the factory).
A long time ago I learned how parts catalogs, and eventually the digital equivalents thereof, actually get written. It's mostly part-timers who have little to no automotive experience or even knowledge, but can type. A solid percentage of those people are/were full-time college students, who'd already had a full day at class and still probaby have studying ahead of 'em. They're paid by the entry, not by accuracy and generally aren't double-checked. Our system, as well those of O'Reilly, Advance, and Autozone, will occasionally ask you if a particular early 2000s Ford car has four-wheel drums! It's infuriating when you know better, and reveals the dumbass you are if you don't. You've probably been asked equally-stupid question. The computer asks. It's that bad.

Also, there must've been the occasional jokester. We had a catalog back in '90-'91, I think it was maybe McCord (remember them?) or Victor. It listed a "Humber Super Wombat" that was available only in a two-door sport coupe or eight-door limo. It also had an outrageous engine choice, like either a 1.5 L4 or 10L V8--nothing between. There were part numbers and the whole nine, but back then you could only check the viability of such things by ordering and seeing if they came. Humber was real, and had a model called a Super Snipe, but with neither engine. The Super Wombat? I've never found any reference to it other than that one catalog 30+ years ago. Bummer. We thought it was the best car name ever. :D