1968 D100

I swapped my AMP gauge out for a Volt gauge a while ago after a dash harness failure. I realize now that it would be nice to have that function back.

My question is, can I run an aftermarket gauge pod from the fuse box Alt wire connections and see a true reading? Factory basically routes the wire through the gauge and I am wondering how I can reproduce that without hacking into my nice harness which I have ran a constant wire in place of the spliced connections for the old gauge.

Thanks!!!