a 90` hatch is obd-0 which you can use the same harness in the hatch with the LS. your best bet is to get a p28 ecu, chip it with a LS base. And purchase an obd0-obd1 conversion harness. you want to run wires off the obd0-obd1 conv harness for a o2 sensor as well (wires are supplied), if you dont plan on using a stand alone o2.