MSD to 340

If you arfe wiring the MSD per the instructions you are hooking the small red to the + wire of the coil. This wire is just used to turn the MSD box on and off with the ignition and has no impact on the actual function of the MSD. Whether ryou have the ballast in or not makes no difference but since MSD gives you a jumper that allows you to bypass the ballast why not elimiate a potential point of failure?

NOTE: if you decide to go with out the ballast hooked up you will need to jump the two sides together. One side (with brown wire) has power when cranking and the other side has power in the run position. You will have isssues getting the engine to start or stay running if ther are not jumped.