There were two flavors of rear discs that found root in the Avanti. One was Jim Turners and other was Dave LeVesque. Both similar and very functional. If yours has the GM mid eighties caliper ( Cadillac, Riviera, Toronado), then they are likely one of these. There are other third party kits which use similar components. I don't know what you mean by the calipers riding high. Is it, that the pads are off the rotor? Whatever, none of the Turner or LeVesque products have any odd look to them. Pic below is an old
shot of mine (late 1990's) and the pad sweeps most of the rotor (Lincoln rotor)