loss of power while driving
Well of course it COULD be a bad ignition switch. Run some tests when you get time
Find ignition power under the hood. What are you running for a system, IE points, Mopar breakerless, MSD, etc.
Unhook the ignition box or make sure the points are open so you don't burn up the points or the coil , / box.
Clip your meter to the ignition buss so you can watch the meter. Wiggle the bulkhead connector. Wiggle the ignition switch connector under the column. Wiggle the switch itself.
Notice the voltage and compare to battery voltage, what is the difference voltage?
Then move the meter down to the ignition switch connector where it comes out of the column and check that for damage and intermittent connections.
You can download a 72 service manual fer free right here:
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
Also read this article on the problems with the infamous bulkhead connector
http://www.madelectrical.com/electricaltech/amp-gauges.shtml