Help! SBP to BBP and need help finding BBP Drums

Since you had trouble sliding them on, the binding is probably at the diameter. Can't do much more than have a 10.000"ID on the drum. A lot of people have had tight drums after a rebuild, when using factory parts. It seems some replacement self-adjusters are a bit too long. You might file the slots in the shoes slightly to compensate. You could also just drive around slowly, applying the brakes, and see if they loosen up after initial seating. If not, don't drive far or they will quickly over-heat your whole rear-end.