You are missing the point
@Blackwater, in the year differences between the trucks. You can't just "swap" a 92-94 cluster with a tach into a 88-91. Richard pointed out the big differences....
you say "I mentioned that they could be swapped. I know this cause I have done this to others. Schematics are all the same, pin layout and connectors differ."
The wiring is the same (largely) with the same connector 88-91. They entire setup changed in 92-94 with a new plug style and the speed sensing equipment was moved external to the cluster.... so no, the schematics aren't the same... Plugs between the two style vary greatly.
I have an 88, I converted it to 92-94 style wiring with external DRAC and a 454SS cluster... Not a simple task. Yes it can be done.
I think the definition of something that is plug and play, a swap or something that is do-able isn't really defined the same as it is for myself or Richard, although I get what you are saying.
Lets calm down with the attitudes now.