ok to convert 10 x 1 3/4 drums to 11 x 2 1/2 on '72 dart?

Good grief those brakes are expensive!!!!

I paid $80 for a set of loaded 11x2.5" backing plates from another seller on eBay. Yeah, I still had to buy drums but those are like $50 a piece.

But yes, with a set of 11x2.5" brakes and a set of BBP axles you should be fine. Call DrDiff, he'll set you straight.