So, I picked up rebuilt calipers the other day, and this morning went out and started installing them. Did the left front, no problem. Opened up the box of the right front, and immediately noticed that the new one was missing what looks like a heat shield against the pistons. Opened the other boxes for the rears, and both of them were missing the heat shield. Haven't pulled the rears off yet, so I don't know if the original ones have them or not. The new one for the left front DID have the heat shield.
How critical is this part? My parts house is in the city 80 miles away, so I can't just zip down there and grab another caliper. And the heat shields on the old ones are all rusted up and won't come out.