The main reason these drums are obsolete is the wheel hub pattern you mentioned: 6 on 7.25".
This massive 6-lug pattern is highly proprietary. Aside from vintage IH 3/4-ton trucks (and a handful of very early Dodge and Studebaker heavy-duty trucks), the automotive industry completely abandoned this bolt circle in favor of the standardized 8-lug (8 on 6.5") pattern for 3/4-ton and 1-ton trucks.
Because the market for this specific drum is so incredibly small today, companies like Raybestos, Bendix, and Centric have long since scrapped the casting molds.
While the cast-iron drums are missing in action, the internal components for the Bendix drum brakes inside the RA-10 are still readily available! Because Bendix used standard sizes across multiple brands in that era, you can still easily source:
Brake shoes (usually 12" x 2.5" or 12" x 3")
Wheel cylinders
Springs, adjusters, and hardware kits
Are you currently trying to get a vintage Travelall or 1210 back on the road, or are you just weighing your options before starting a restoration?
