Lincoln Brake Conversion issue

[mullskull]

I'm in the middle of doing a brake swap on my roadster.. swapping the 42-48 ford drums and backing plates for a pair of original 1941 (flat) lincoln drums and (shallow)backing plates.
My car has 42-48 ford spindles..
All the parts are restored, and all brake components are oem style purchased from Boos..

The drums won't seat into the backing plates.. they are about 1/4 - 3/8 out too far.. they spin freely, just not in far enough. They way they are now about an 1/8 of brake shoes aren't inside the drums.
Right now the bearing and races are the same as early ford.. (timken # 15118 bearing #15250x races).
The only thing that makes any sense is that the 1941 lincoln drums use a narrower inner wheel bearing ?
Would anyone know if this is true?

Just for the heck of it i check the fit of the ford drums..and they fit just fine on the newly set up lincoln backing plates.