Ignition start / run question

Car is a 73 Dart 340 Sport. Trans is a Chevy 200-4R with B&M Megashifter. Engine is just broken in and I'm still in the middle of doing all the normal checks to make sure everything works. Converted the 4 pin ballast to a 2 pin, new Mopar chrome box, new voltage regulator, and new starter relay, new ignition switch. MAD bypass was done, crackedback's headlight upgrade and heavier alternator wiring kits installed.
When cranking, the engine spins as it should but doesn't seem to fire until the point when I release the key and it drops back to RUN. It starts right up then, just when the key begins to move from the START to RUN position. Any suggestions appreciated.