Paul
If the original SSBC kit used stock Impala ss rear disc brakes to add to a fleetwood, then you can get loaded calipers, and rotors from Rock Auto. The loaded calipers I got from them not only had the pads, and guide pins, they also had the mounting bracket for the rear calipers. Took a couple days to get them, but I am sure they offer overnight delivery if you order them today.
calipers
rotors
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1980 Cadillac Coupe DeVille. 6.0 87k
2017 Chevrolet Silverado LT 4.3 Aluminum V6 (My daily)
2008 Saab 9.3 convertible (Wife's Daily)