your truck will have a tac wire.. so there for it has a tach signal going somewhere.. i bet theres something behind that cluster...

all vehicles have a tac wire if they have some sort of ecm pcm

 

I am A John Deere Mechanic and see enough wiring harnesses to know that mostly manufacturers want to use as few different harnesses as possible. I was looking at an excavator today that seems that it has more empty plugs than it does used plugs. So I am betting that the wire is there. It also seems to me from reading here, that no one hese has done this upgrade. Tell ya what, if someone would pull their tach cluster and ship it to me, I'll try it out and see what happens. I promise to get it back to you with-in 20 years.

I did notice a section devoted to wiring diagrams, so I think I will go check that and see if I notice anything. There is also a classifed section, so maybe a note there is in order as well.

Thanks for everyones' input and maybe this bump will get seen by that one other idiot that did this upgrade and s/he can tell this idiot the specifics on it.