Thanks everyone. I didn't think to bench test the new switch before installing it. I will next time! The wiring is straightforward, switched power from the ignition switch to the resistor, single wire from the resistor to the positive post on the coil. I installed a single wire from the side terminal of the new starter switch to the positive side of the coil.

When I got the truck there was a ballast resistor that had been bypassed. The coil, though working, had a deformed top and was leaking. I bought a new Delco coil and the new ballast resistor to match it. I don't know if the new coil is internally ballasted, so that's something I'll have to find out. With the ignition switch in the off position there is no voltage to the resistor but there is power present at the side terminal of the new starter switch. My understanding is that the side terminal is supposed to provide a full 12 volts to the coil only while the starter is engaged. Right now my coil is getting power and heating up even when the switch is off.

In a effort to get the truck started I disconnected the wire from the side terminal to the coil, bypassed the resistor and wired the switched power directly to the positive post on the coil, effectively restoring the original set up that was working with the old coil. I pushed on the stomp starter and the starter didn't turn, though I could smell something getting hot. So there may also be a problem with something other than the new switch. I can put the old starter switch back on but I'm not looking forward to that job with much enthusiasm!

That was enough for me for one day!