Having a fit with the passenger's drum on '67 Dart

The shoe lining should be longer on one shoe than the other (primary/ secondary) is it possible that you got two primary or two secondary shoes together on one side?

Are you absolutely sure the cups are bottomed out in the cylinder, and that the pushrods aren't hung up, etc?

Sometimes this stuff gets "cocked" on the backing plate, and you have to grab the whole "assembly" of shoes and wiggle 'em around to get them "seated" where they belong on the backing plate.

Have you tried swapping the drums left/ right? (Just to try the fit?)

It might be possible that you have an iffy pair of shoes, that is, damaged, bent, even a wrong shoe, or someone put the wrong lining or did not properly arc them.