You are going to have to trace back from the coil positive the rout the power goes all the way to the battery or the first point you do have power along the route.
You are going to have to trace back from the MSD box positive the rout the power goes all the way to the battery or the first point you do have power along the route.
I'm assuming you loosened the steering column and moved it some amount. The power to feed the coil basically goes as follows.
Batt positive to starter relay post.
Starter post to fusible link
Fusible link to bulkhead connector
Bulkhead connector to ammeter
Ammeter to main splice
Main splice to ignition switch
Ignition switch to IGN 1 (run) and IGN 2 (Start) (because you can crank the engine we know you have power to the ignition switch)
Now you need to check that you have power to IGN 1 with the key in the run position, go under the hood and locate the ballast resister that you may have bypassed to add the MSD box look for blue with tracer that is IGN 1 and with the key in run should have power.(No power there look at the bulkhead connections "N") And the IGN 1 terminal on the ignition switch)
Now you need to check that you have power to IGN 2 with the key in the start position, go under the hood and locate the ballast resister (that you may have bypassed to add the MSD box) look for the brown wire, that is IGN 2 and with the key in start that should have power. (No power there look at the bulkhead connection "Q") And the IGN 2 terminal on the ignition switch)
As I stated before you need to also trace where you are getting power to power the MSD box I have no way to know where that is coming from.
Then you need to go to the coil positive and see if you have power there in both run and start.