Master shut off switch charging problem

Mattax said
I'm not clear why its important to be hooked to the ammeter in this situation.

If you want to use the ammeter then my suggestion is use it only for battery charging. Then it will read correctly, and not be carrying extra loads.
And if you want to do it with just one fusible, then something like this should work. Use a grommet through the firewall (or some other substantial firewall feed).
The MSD heavy red wire can connect at the terminal as can the fuel pump.
View attachment 1715539630

the other guys may see faults or drawbacks here.

Thanks Mattax, it’s not the ammeter I care about, its power to the fuse box. I do like in the schematic running the ground side of the cv relay through the master switch. That will cut down on a lot of wiring.
I answered my own question about relay current draw, it’s about 1.3 amps.