If your original wires weren't butchered in the motor swap, the wire you need should still be there,ready to use. Closest manual I have is 86' Pontiac and it looks the same as all others I have seen. With a 3.8 and no gauges, the "engine oil pressure switch" gets a hot 12v brown wire from fuse block (C/H). It is piggy-backed to another brown wire that goes to the computer. It may or may not join exactly at the switch. On the other switch terminal, is a tan wire from the "engine oil warning" light on dash. That is piggy-backed to the wire you are looking for- the light blue choke wire. Those 2 WILL be joined at the switch terminal. All of these wires should be found on a female connector that has 2 cavities that belongs on the oil pressure switch. Look for the connector and there is your pot-O'-gold. If connector is missing, look for the stray light blue wire. Then you just jump the 2 terminals, and the car thinks there is oil pressure so the choke heater works.