From what I've read, there are no OEM replacement rear bushings for 88. There are no ball joints, so all you have to deal with are the bushings on the rear suspension links. Those links were replaced as a unit with bushings already installed, so I don't think you can get replacement rubber.
You can get a poly bushing kit for it; however, so if your bushings are shot, that's an option.
The poly kit is available from Summit Racing. Part number: PTP-7-305
Use PN: PTP-7-305-BL for black bushings instead of red.