MSD 6AL ignition box

Hey Guys,
Hoping for some help here.

I just installed an MSD 6AL ignition box in my '71 duster. I checked that it is wired correctly, though it took a bit of searching to realize that ther isn't supposed to be power to the coil. I did the spark test as outlined by MSD and it all checked out - great spark from the coil wire to ground when shorting the trigger wire.

Problem is I don't have spark at the plug. I called MSD and the only thing they could come up with is that the box wasn't getting enough voltage during cranking. I checked with a voltmeter, got 12.4V with the ignition "on" and 9.4V while cranking. The tech said to try to keep the voltage above 10V when cranking. So while I charge the battery back up to 100% I was wondering if there were any other possible issues I am missing.

The car fired and ran fine with the mopar electronic ignition before doing this swap and as I said the wiring check out as per the spark test. The distributor is new (came with the mopar performance electronic ignition kit) and the rotor spins while cranking.

Any thought?

Thanks.