[tbplus10]

I've seen 1 in dash tach for that bodystyle, on a 87 Chevy truck. And I'm not sure it was factory, I think the gauge package was custom made.

 

[tbplus10]

but the guy did bring up a point... The wiring harness for the new IP would probably be different from the existing wiring harness.

If theyre the same year model trucks the harness will be the same. Ever notice all the spare plugs on a wire harness? One harness is used for all aplications and options possible on that year and model.