Which one? MSD AL6 or MSD AL6-2 for my stroker 418 (340)

MSD has a pdf catalog online you can download that will show you how to wire just about any set up you can imagine. As far as the 4 pin ballast - a jumper wire between the female ends of the ballast connector that would connect across the top and that's it. The ballast is there to limit voltage to the coil and since the MSD typically does not reduce voltage to the coil the jumper does that. There are two styles of ballasts - a 2 pin goes with a factory ecu that uses only 4 of the 5 pin outs on the ecu. The 4 pin ballast and extra wiring is for use of a 5th pin on the factory ecu. For a 4 pin ballast connector set up using the msd you want to jump across the one ballast connector that has a loop to itself top and bottom, to the other ballast connector whose wire does NOT go to the 5th pin on the ecu.

http://documents.msdperformance.com/catalog_wiring_diagrams.pdf