Found a Source for 10” rear drums with 1-3/4” shoe
Last I checked Raybestos/Dana corp still makes the drums and small bolt disc's. They go by Brake Parts now up in McHenry IL if someone wanted to look them up.
I went to the following website which as stated above:
http://www.brakepartsinc.com/products.php
When using the PRODUCTS feature at the previously listed website, if you select DRUMS, you are re-directed to the Raybestos website and you can select your MAKE, MODEL and YEAR, then SEARCH using the online CATALOG.
When I selected DRUMS for my 1971 Plymouth Duster 340 (it is a factory 340 Duster - VS29H1B), the only DRUMS listed as available were the 9" inch variety.
There was no listing available for 10" inch rear DRUMS for either a 1971 Plymouth Duster or 1969 - 1971 Dodge Dart.
If Raybestos still makes the 10" rear drums that work on the SBP 8 3/4" rear axle found on the factory 340 cars from 1968- 72, and some other Abodies of that period including V-8 equipped and police units, it is not listed on either the BRAKE PARTS INC or RAYBESTOS websites.
I did find that Rock Auto AGAIN lists the Centric 123.63044 part as available so they must have received another shipment.