[VetteVet]

The basic thing you need to remember is that all your key off power sources need to go to the same distribution center. This includes the alternator with the engine running of course. Then you can feed all of your loads that are key off, Headlights, hazards, courtesy lights, etc.
Then you can feed your fuse panel and your key switch to activate any relays, ignition, accessories from there. Your alternator will be the main source of power once the engine is running, and the key is on.

You do not have to run the large battery cable to the distribution center (main junction), as long as you run at least an 8 gauge wire from the battery positive to the junction for engine off, key off power. Most of the post 74 trucks used the positive post on the starter to run power to the truck through fusible links.

If you plan on keeping the battery gauge instead of a voltmeter then you will have to wire like the factory did.

I highly recommend using relays for the fuel pump, the headlights, and the key switch to take the load off those items. the starter solenoid is also a good candidate but the key switch handles it well because of the short time it usually draws current.