Well I'll go ahead and assume you have a foot starter even though many people don't tell us if they have something different than stock. I am speaking of a Chevy system in 1947. GMC manuals are hard to find. Again assume to be the same. (except for positive ground systems). If same as Chevy otherwise, you will have a reversing switch mounted on the starter. This is before ballast resistors were used. It "saves" the points. If you have that, disconnect for this start up.
Here is what you need for start up. Do not connect anything else. Disconnect everything. You are not using the ignition switch for this. You will not have a charging system or any gauges. You ARE NOT using ANY of the wiring harness per my list.

I DO NOT KNOW IF YOU HAVE A POSITIVE GROUND SYSTEM. GMC USED POSITIVE GROUND UP TO ABOUT 1956. The following hook up should be OK anyway.
If you decide to leave it Positive ground, DO NOT use this info....or reverse the info.

1. Positive battery cable to starter switch big lug. The starter switch is mounted on top of starter.
2. Negative battery cable to starter mounting bolt or a motor bolt.
3. A new positive wire from battery to coil positive. Use this, as you said to shut motor off.
4. I have to stop here and wait for someone else because the original distributor has two hook up spots for this idiotic reversing switch and I don't know which receives the coil negative/how to bypass the rev switch. Probably either distributor terminal can receive neg coil wire.

If your GMC has been updated in these areas, now is the time to explain so that Jerry and others can give you the correct info for a test start.

All of your profile and user name says 1948. You post says 1947...which is it? BIG DIFFERENCE for this discussion for Chevy. This was a transition year 47 to 48. No more reversing switch, electric solenoid option, etc. Both years use the externally resisted coil.
Don't now what Chevy did after reversing switch and until side terminal/ballast resistor? 55.1


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