MSD Install While Keeping Orange Box?

You would have to do some rewiring in order to do this, and probably the easiest would be to come up with some nice weatherproof connectors, so you can unplug one system and plug in the other

What you'll need to break and make

The connectors will have to replug the mopar distributor from the MSD to the Mopar

You'll have to switch the power at the ballast from the MSD to the Mopar. You'll need to leave the ballast in place to make this easier

You'll have to break both coil neg and positive to switch them from the MSD to the Mopar

There are various ways to do so

I would take a completely different approach. I would buy a "ready to run" import dist, a spare coil, and learn how to quickly switch them. "Rig" them so that you can easily connect them "hot wire" fashion. In fact, years ago, I actually had a Mopar dist. with a coil mounted on the side, and a ballast. It was, in fact, a completely integrated ignition in one big piece. You could slam it into an engine, hook up battery power, and have ignition.

Still another approach is what I'm doing now. I have a small box with an HEI module and a coil. You plug it into a mopar breakerless dist. hook up clip leads for ground and battery, and the high V. coil wire, and "you have" ignition

I originally threw this together to test fire some used engines, and then realized "what I had" LOL