I want to install the dash cluster w/tach, (from a 91, I think) into my 88 reg. cab 4x4 w/3,9 and 5 speed. Is there an existing wire that i can use or take one from existing circuit that I don't need? Any advise on the swap would be appreciated.

 

I know with the 92-up gauge clusters, with and without tach are interchangeable. The tach wire is there on non tach gauges. I'm not to sure on the early years though. I would suggest to spend some time with the wiring diagrams in the FAQ and find the wire and test it to see if it live.