when did they go to electronic ignition?

ScampMike said
and it may have been an option before that..

A body 1972 340 got electronic ignition, 1973 all. Not available before 1972.

It seems all 1972 V8 got electronic ignition in the fall of 1971.

http://www.hamtramck-historical.com/images/dealerships/1972PlymouthOrderingInfo/1972 p pib 10.jpg