You really only need the ignition powered to run it along with the starter wiring. And that hook up will depend on what ignition you are running. But no matter what ignition you have, it is a simple wire or two. I use the black lead on some jumper cables for the heavy ground for the starter. You will likely need the alternator on it to drive the water pump. But you don't have to hook it up if you don't want to. Running the engine will draw very little juice. The only real draw will be the starter when cranking.

Personally, I do not power up the alternator during pre runs. Just more wiring to mess with and the outside chance of something going to ground when you don't want it to. If you are concerned about battery voltage when running dead loss, just hook up a battery charger while it's running. That's what I do. I just want the bare necessities during pre runs. I usually just use jumper wires for the ignition hook up and the starter wires for the starter. And I just hook and unhook the power jumper wire to the ignition for the on/off switch. Simple and fool proof.

A mechanical oil gauge is a must. I just have one on a short brass tube or hose. No need to mount it anywhere. A temp gauge is optional IF you have a temp gun which I like to have there anyway.

Do you have a priming rod?