There should be a smallish wire (8 or maybe 10 gauge) from the battery cable terminal at the starter, going into the cab. That supplies battery voltage to the ammeter. Disconnect that wire and leave it loose for now. That will isolate the entire original electrical system and allow you to power up nothing but the ignition system with the wiring setup bartamos has described. That will keep from getting a "positive smoke check" and possibly a fire in what's left of the original wiring harness. For a test run, you don't even need a radiator or a fan belt- - - -just plumb a garden hose to the water pump inlet and run a small volume of water from the hose out of the thermostat housing. (Remove the thermostat) I have run engines that way while strapped down on a forklift pallet for extended periods of time, checking for oil pressure problems, rod knocks, etc. Good luck!
Jerry
