Hey Drew, Good to see you around.
Couple of things I've picked up on, disconnect the tachometer if he has one, a bad one can ground the ign.
As stated before low battery or voltage drop in the wiring will cause these aftermarket ignitions not to work, if the battery checks good try a jumper wire from the battery to provide temporary power.
I recently was troubleshooting a GM truck that would shut down after heating up, turned out to be a bad coil wire. Pull the coil wire from the distributor & see if it will arc 1/8" to ground when cranked(make sure no gas is around)
Good Luck
Wade