It is so hard to figure out what goes where on those. The big plugs are easy, or course. With a tach, there is a single wire to it, and a 3-wire harness from it to the small diameter clock. If you can't figure out where a wire goes, it's best to leave it loose and see what doesn't work, as hoooking in on to the wrong thing car fry the cluster, part of it, and your wallet.

Can you get to a junk yard and have a look?

Good Luck,

Bob

;>)