Installed new coil, now the tach acts funny

Radio condenser belongs on the + PLUS

"Bare end" Look at the photo you posted. Hard for me to see, but I believe the upper end goes to the engine bay, the bottom goes to the dist. If you separate those two, the engine bay end will have a bare male end sticking out, and the other will be recessed, female, insulated The bare end is the "signal." This is in fact a test point for troubleshooting. If you lose spark, you can tap that bare end onto engine ground (with key in "run") and it should generate a spark each time you do so.

To repeat, make certain the proper wires from ECU are actually connected to coil +

So..........Coil + PLUS should have proper wire from ECU, the radio cap if used
Coil NEG should have tach wire (normally) and the proper wire from ECU, normally black

And if that is correct and tach does not work, "try" the jerry rig to the dist. connector I've never heard of this, ever. Just did a quick search, tho, and found some references from MoparChat and B bodies only