People that make harnesses should be able to get right pins to put in C500 and C200 even tho the bodies are hard or impossible to get as new parts.
Might find old spare bodies and install new pins.
GM use same pins for most Packard and other plug formats.
You don't want pigtails for major work. Every splice is more to hind and often adds more problems. If not now, can fail months later on the highway.
Even when the splice is good and "water proof" the splices can make stress point that break the wire more easily.
"Water proof" is often temporally at best. Any small hole and water get in it causes big problem. If not now freezing heating and chemicals can open most things then water get inside.
I try to avoid them for many things but new "Pull to Seat" Metri-pak pins used for some later Fiero sensors and similar make this impossible to almost everyone.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave