[WestButteTruck]

I've done a fair amount of research on this and the 98 3 wire temp sensor seems like a proven method with accurate results. I have parts on the way to do the same. They do have adaptors available for OEM senders that can be used on the rear passenger side head. But, with the cost of the sender and adapter, I was in for about the same amount of money. I should also mention, I am working on a 1984.

Temp sensor - ACDelco 12551708
ACDelco 3 wire pigtail 88862238, the blue wire goes to the temp gauge.