I think the change came going from the 84 to 85 model years. My 5 parts car doesn't fit the 85. There are wiring diagrams available but I haven't checked the details. car-part.com is the retail side of the junk yard online sales system. They don't care about cars this old but you may be able to locate some cars near you. That part was used on several models of that era. Someone here may have one.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.