[87Skier]

The early F-body cars with LS engines used a 3 wire temperature sender. Two of the wires go the ECM, and the other is a standard temperature gauge. This was later changed when the instrument clusters started using the reported signal from the ECM.

ACDELCO 12551708, is for a 1998 Camaro with the 5.7L. The picture clearly shows 3 pins in the sender. Most only have two.

I used a 147 ohm resistor, but would recommend something closer to 155 ohms.