welcome to FTE... Depending on what wiring you lost to the mice/rats you can probably be safe pulling a harness from another 87/88-90 EFI 302 or 351w with XL or XLT package b/c it has the AC wires for the compressor. Keep in mind EFI was new in 87-88 so the wiring for the SD EFI systems weren't integrated into the truck harness fully until 89-90...