[rich b]

Those modified '40 hubs will work with the Buick drums in conjunction with F-2/F-250 backing plate assemblies.

As you found the offset of that combination is incompatible with the Lockheed backing plates.

The Lockheed plates are deeper than the F-2/F-250 plates.

If you want to use the Lockheed plates; you will need to get and machine a couple of the '48 style hubs where the flange is outside the drum; like Skidmarks described above.

Or, source some F-2/F-250 brakes which are Bendix self-energizing (better) brakes.
Probably again in the next couple days or so.

Someone lists rebuilt F-2/F-250 assemblies in the Ford Barn classified from time to time.