I have a '60 T-100 that had a problematic Franz.
(turned out to be loose magnets doing a maddening vibration dance....the last place I looked!)
While getting that sorted out, I had a "would this fit somehow?" moment and installed a low wind P-90 as a placeholder.
As Walter mentioned above, the dog ear cover screw holes and the mount tabs lined up perfectly with the Franz cover holes. The body of the pickup fit the cavity well. So no modifications at all....which was important to me.
I don't have anything with a LB-1 or humbucker.....so can't help with info about coverage.