B body brakes on A body?

There I learned somthing about the later B's, thank you!

If your wanting to stay with the original 14" rims, not all is lost. Sell the bracket for the larger disk brakes as people are always looking for them and just get a bracket for the smaller, off any F, M or J car up to 1986-7 as they are very easy to find and they bolt right up to the spindle. Of course you will need the smaller rotors too but the calipers are the same regardless.

PS I'm also not sure about which flex hoses you may need for the setup but there are write-ups on the subject here on FABO too