Many of the internal parts interchange on the BW units such as blocker rings, planetary units and roller clutches. The parts that do not interchange are specific to the OEM such as housings, mainshafts, etc. The R-10K unit that I have is here for repair. Initial inspection reveals that it is the same as every other GM OD I have rebuilt over the last 40+ years. I had not seen the K designator before or not paid attention to it.
The solid shaft on the clutch gear is probably a Warner replacement part.
There is a GM oddity out there that was used in 64-65 in a Chevelle. It uses the same BW unit but the mainshaft and all the internal gears have a different pitch. None of these parts will interchange with the conventional SM318/319 gears.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine