I would start with Steele Rubber Products (NC). If there’s any kind of core to the bushings (not sure if there is as I’ve never removed mine) they will revulcanize them. Also, check their catalog and Cars,Inc’s Buick catalog. I would almost guarantee that the F-85 and the Buick Special and probably the Tempest from 61-63 would share the same bushings, and my experience tells me the Buick stuff is always more available. If none of that works, check the part number vs. the Corvair. They repro everything for the Corvair, and it might be a match.