Would like to upgrade my instrument gauge panel

[ManzanoNissan]

Hey all, I've got a 1991 D21 4x4 (4 cylinder) and it has an instrument panel without the RPM gauge. I'd like to upgrade with something like this. https://www.ebay.com/itm/126173999965?c ... vA13w7dfHk
As the speedo measures RPM into MPH, in theory can I just slap this baby in and have no issues?
Is there a way to advance the mileage meter as well? Although to be honest I'll be rebuilding the engine next year so....not sure that's a big deal to have matching mileage showing.

[VStar650CL]

The speedo is measuring driveshaft RPM and not engine, so the tacho and speedo/odo are only tangentially related to one another. The clusters from back then all produce 2 pulses per rev internally from the speedo cable, but the needle calibration may be different from your existing cluster. If the speed is off, you'll need to change the speedometer gear. The tacho gets a digital signal from the ECM (ECCS in the diagrams), but I don't know if the wiring will be there or if the signal will be present from an ECM with non-tachometer software. If the wiring is absent you can string it, but if the software is wrong then you need to work around it with a tach adaptor taking signal off the coil, something like this:
https://www.ebay.com/itm/141931549970

[ManzanoNissan]

The speedo is measuring driveshaft RPM and not engine, so the tacho and speedo/odo are only tangentially related to one another. The clusters from back then all produce 2 pulses per rev internally from the speedo cable, but the needle calibration may be different from your existing cluster. If the speed is off, you'll need to change the speedometer gear. The tacho gets a digital signal from the ECM (ECCS in the diagrams), but I don't know if the wiring will be there or if the signal will be present from an ECM with non-tachometer software. If the wiring is absent you can string it, but if the software is wrong then you need to work around it with a tach adaptor taking signal off the coil, something like this:
https://www.ebay.com/itm/141931549970

Hey I appreciate that information. Clearly not an easy switch out. I think I'll focus on finding an upgrade that was made for the model first before taking this route. Thanks!

[VStar650CL]