Gauge voltage and Fuel relay with AA classic install

Hellllllooooooo FABO electrical wizards!!!

I have never totally wired a car before so bear with me please.

1967 Barracuda Fastback rallye dash/gauges/American Autowire 'A body classic kit'

Question #1
When I tested guages I used 3 AA batteries to check sweep and check weather the things were gonna register anything. Now they are in the car and Im thinking to myself as I look for good grounds for everything.....where does the voltage step down for the gauges? If there is something I am supposed to splice into the power feed to gauges....what does it look like?

Question #2
Holley Sniper EFI in the same car. There is a 12 gauge blue wire with a relay and fused located about at the firewall that runs to the fuel pump located around the axle. So, give or take around 6' of wire. I was always told to run the relay as close to the unit that was going to be powered up. I have a universal summit fuel relay handy and it has a little metal box fuse looking thing that comes with it. My super safe voice in my head says "Hey Clem, go ahead and use that blue 12 gauge wire marked 'fuel pump' and trigger a relay real close to the pump". This car has the battery in the trunk so everything is in close proximity for this situation. Do the voices in your head concur?

Thanks FABO!!!!!