7.25 to 8.75 conversion 1974 Valiant

Yeah there’s no way I’d use re-drilled axles without already having a complete SBP brake set up in hand.

And as the professor said, SBP brake stuff isn’t always available, it’s dropped out of production for years in the past. I’d just get the proper BBP axles and run the BBP brakes you’ve already got. More braking surface and much easier to find parts, and you can use everything off the shelf. With the SBP drums, every time you need new drums you’ll need to have the BBP pattern drilled before you can use them.