Brake swap caliper question

And you can get calipers at any parts store or on RockAuto, they're readily available in both piston sizes.

plus they are pretty inexpensive. last set I bought were about $20 each new and some even come with new copper washers. 1980 Aspen/Volare is a good one to get.
Do check the boxes to make sure you get a left and right, dont trust the labels.