What you describe is exactly what happened. Got the drums on, rotating okay, then tightend the screws and the drums wont rotate. I think I might try swaping drums side for side, as suggested above, out of desperation.
All wheel cylinders are okay, replaced one that was not. I beleive the diameter of shoes is fine. Kicking myslef for throwing the old ones away so eagerly, but they were oil contaminanted so no use even as spares.
Springs are in order, adjusters backed out and seem to operate correctly.
Meantime if someone has correct measurment for width of shoes (front of 1976 109) that would be useful.