How many variations of pin and wiring layout exist for C500. I am putting a V6 in a 1984 car. Everyone seems to have a different take on what is powered or senses through C500.

I can't quote specifics, but the 84, in general, is quite different from the later cars, in terms of wiring. ALL of the wiring.
C500 is not even in the same place on an 84, as the later cars. (84 has it on the firewall. 85-88 has it in front of the shock tower next to the battery.)

Find the factory wiring diagrams for donor and recipient cars... They've been .PDF'd by now, but finding your specific year may take a little work.

84 C500 is completely different then all others and on fire wall.
Worse has output from the alt after f-link A. All later years has main + power "box" under C500. See my Cave, Alternator Sense

85 C500 is different mainly for light side plug because 85 didn't support Fastback lights.
Later years are mostly same.
All are between battery and strut tower.

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(Jurassic Park)

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