I don't have any idea why a relay would be called for in this scenario, but I would get rid of it and just run a a wire directly from the ignition switch to the ballast resister then to the coil when you put the truck back together.
Is this a fresh rebuild with a new cam and lifters with zero hours on it?
If so, you will need to pull the distributor, prime the oil system through the distributor hole, then reinstall the distributor. Then you will need to start the engine and immediately run the engine at 2,000 RPM for 20 minutes to break in the cam.
I recently did what you are getting ready to do. I used the gauge cluster and hooked it up so I could monitor oil pressure and temperature during this critical nerve racking break in procedure.
I used a small plastic boat fuel tank including the priming bulb for fuel supply.
You will want to rig a way to quickly disconnect power to the coil so you can shut the engine down should something goes south on you.
Carl
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