Understanding what MSD has to say is going to be a key to this issue. You need to go to the MSD site and download everything you can find about their "box."
As said above: and........
There's a white wire used to trigger points. You can tap that to ground and produce sparks to test. Make sure the white is NOT grounded when trying to run normally. I can also be used that way (grounded with a switch) as an anti theft
There are "two" power wires. The "big red" is a heavy power wire and is intended to be wired "hot" at all times, like to the starter relay stud
The "small red" is a relay trigger wire. This is what is to be switched 12V. THE PROBLEM many have is they don't get the ballast properly bypassed, and DO NOT get power "in start." There are two original wires, one is "run" and one is "start bypass" Those must be connected together