Cluster interchange issues

[75Monza]

Looking at installing a stock cluster that has a tach in it (was for gas, not diesel) with 100mph speedo and small fuel gauge where the clock would go. This would be into my '80 K30, auto with factory gauges (no tach), just the above basic Scottsdale trim.
1. Will an '81-'87 cluster bolt in the dash on an '80?
2. Would there be any differences in the pin out of the plug?
3. Would I need to add the wiring from the plug out to the HEI for the tach, or did the harness under the dash at least have that to the firewall at least?

Since this is going to be my plow truck, I prefer having a tach that I can see RPM while I'm plowing since I'm dropping the 454 in it. Got so use to having rev limiter on my old '73 ford F250 plow truck to give me a heads up that I'm at the throttle limit, don't plan on putting anything like that on my K30. Fall into the trap of admiring the sound of wide open through dual while plowing, sort of loose track of what I'm doing, lol.

 

[C10MixMaster]

Looking at installing a stock cluster that has a tach in it (was for gas, not diesel) with 100mph speedo and small fuel gauge where the clock would go. This would be into my '80 K30, auto with factory gauges (no tach), just the above basic Scottsdale trim.
1. Will an '81-'87 cluster bolt in the dash on an '80?
2. Would there be any differences in the pin out of the plug?
3. Would I need to add the wiring from the plug out to the HEI for the tach, or did the harness under the dash at least have that to the firewall at least?

Since this is going to be my plow truck, I prefer having a tach that I can see RPM while I'm plowing since I'm dropping the 454 in it. Got so use to having rev limiter on my old '73 ford F250 plow truck to give me a heads up that I'm at the throttle limit, don't plan on putting anything like that on my K30. Fall into the trap of admiring the sound of wide open through dual while plowing, sort of loose track of what I'm doing, lol.

Physically all clusters interchange 73-91. pin out varies between years and gauge/idiot lights. Tach has its own separate harness.

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[75Monza]

Sweet, thanks for the pin out! I was looking at the back of a cluster with the tach and just noticed that there are separate wires to it. Was just going to do a tach on the column or dash, don't like the look though.

 

[Green79Scottsdale]

You will need to make sure and run the correct printed circuit on the backside also. When I did this swap on my '79 no repinning of the plug was necessary.