Originally Posted by
greenman100
The best way is to run a cable to the positive terminal of the battery, fuse it at 10A. bring that cable to your gauge installation. split it to a relay. trigger the relay off your radio's ON/ACC wire. that relay connects to the ignition switch wire in your diagram. the other half of the split from the battery terminal goes to the wire thats connected to the battery in your diagram
I'd do this, except something a little larger, with a distribution block inside, and then a small fuse block, relay triggered fed by the dist block, for future upgrades.