Josh, it sounds like you read the manual. You have it exactly right. I am sorry I am late jumping in on this latest discussion. I misunderstood this at first too. I thought the ECU took it's signal from the tach drive of the MDS because that is what the Mega Squirt does. If you go on line to Accel's web site, and go to the instructions, and digrams section of the site, you will find their version of the MSD listed there. I suspect it is either made by MSD, or made under license from MSD.
Anyway, the diagram for how to integrate the MSD(their version is called Accel 6a or some such thing) with the Gen VII ECU is there, and it shows just what Josh said. The MSD box can be fired by a distributor, or by a single implulse on the white wire, in which case the distibutor connections are not used. The ignition harness of the ACcel ECU has a single blue wire which is wired into this white wire on the MSD box, and that is what fires the box, which fires the coil, which lites the plugs which fires the air fuel mixture which was drawn through the valves that were opened by the rockers that sat in the head that Mopar built.
I have everything now wired, and ready to fire. Next I have to see if I can get my lap top to talk to the ECU. If I can, I will configure the file and down load it to the ECu, and see if she will run. I may do this tomorrow night, or I may wait until Sunday morning when I will have time to play with it. (I work on Saturday).