Ammeter to Voltmeter...who does it?

Things you need to know... A solid state regulator grounded to inst' housing only is not chassis grounded until panel is attached to dash with screws. If you turn ignition switch on while panel dangles from harness connectors, or if that regulator looses ground for any reason, it will pass full 12 volts out to the gauges. Some retail regulator packages have ground fault protection built in but... they cost more. If you buy the one with flashing LEDs you may as well mount it near the fuse box or somewhere so it can be seen. It don't have to be on the back of the inst' panel.
Since a volts gauge will need a ground wire also, best to create a ground harness. Anchor it at lower screw at center gauge pod. Male and female terminals for service disconnect about 3 inches of wire beyond the anchor. Best place to terminate this ground wire is behind left kick panel. Best factory example of all this is at the heater case/blower motor ground.
No need to open the fuel gauge to disable that original limiter. Simply lift the gauge and place a layer or 2 of electric tape over that slither of metal on its backside to isolate that limiter from ground. The blue wire with white tracer supplies 12 volts to nothing more than the limiter. So take it out of the round connector and route it to the replacement regulator. 12 volts no longer goes to fuel gauge. 5 volts can find no other path than through the gauge and sender just like the other 2 thermal gauges. Done.