OK, I've finally got this sorted out!
I've got my basic system all wired up, everything is now working except the fuel gauge, I will tackle that another day.
I have not put in the shunt yet, but I will.
I put the big breaker between the battery and the main harness.
I used a relay for the electric fan power and accessory fuse block.
Unless the key is on, NO accessories are powered up.
Yes, you "can" use the original Amp gauge without a shunt, provided that the battery is in excellent condition and well charged.
My Amp gauge has survived several sessions of starting the truck, messing around trying to get lights working, etc.
If the charge gets even a little low, the Amp gauge WILL momentarily pin, on start-up.
No damage so far.
I am going to add the Shunt before I begin to really use the truck.
I've added an electric fan, electric choke, and will be adding halogen headlamps and fog lights.
The truck also has an electric dump bed, so there are plenty of items to easily draw the battery down.
My final decision that if anyone wants to retain the original Amp gauge, a shunt IS necessary to limit gauge travel and prevent a bent or stuck needle.
