72 318 Ignition Upgrade....Which?

There are many igitions now that are light years ahead of the Mopar stuff but I am not sure if thats going to solve your idle problem. Once the motors hot, idling is not that hard for any ingition to do. Its cold idling, WOT and high rpm's that makes it hard to fire. I love my MSD 7al box but I would bet your idle still be rough. I would think vacuum leak, maybe a old hose but maybe even the intake manifold gasket. If you did not do it, I would change it if you can. Even my engine shop screwed mine up, wasn't too bad but after I change it myself to a Fel-Pro print o seal my idle was better. Sure a new spark box would help, Crane , Marroly also make them but you motor should idle ok with a Mopar unit. Have you changed the pick up in the dist ? They do go bad and they are under $20, it might be very old. Thats first, then a new cap and rotor-I like Accel, its all brass.