the cheapest and easiest way to convert your 48 year old motor to electric start
sell current motor for small pile of cash, thus converting motor to cash
open wallet and piggy bank, add contents to small pile of cash, making larger pile
buy motor with electric start for larger pile of cash, thus converting cash to new electric start motor.
seriously, your going to need the starter, harness, charging stator, most likely a new flywheel and a few other odd bits. a newer electric start motor would be cheaper than buying the parts