Tim,
looking at the diagram in the last link, that is of course for running a fuel pump. In your case, you don't need to bother with the NC contact attached to the solenoid as it would not serve any purpose.
The load side supply of the ammeter is actually connected to the BATT terminal of the regulator. You could run a connection under the hood to that terminal, use an inline fuse and feed the NO terminal on the pressure switch.
