'72 disc brakes vs '73

So Ive searched and am not coming up with much, not the best with computers here. What are the differences between the spindles, if any, between a '72 sbp disc brakes and a '73 bbp disc brakes. The reason I ask is my car is a '72 sbp with disc brakes and I would like to put drop spindles on it without having to do the whole '73 front brakes swap but all the spindles I have found are the '73 up style. Would it be possible to use my existing components on a '73 style spindle?

Thanks in advance!


Car is a '72 Valiant 4 door with a /6 if this info is pertinant.