I have a MS3 Pro installed, but not on a LA, mine is on a slant six in a 68 Barracuda,
Currently have the MS3 controlling fuel only with a mopar electronic distributor running the spark, just recently swapped from a HEI 7 pin to a MSD module, and plan to make the move to MS3 ignition control, using a lean burn distributor as you also mentioned.
2016 2 Feb 68 Barracuda rails and throttle