If the RC church had allowed this in the 70s I am certain that a good number of Catholics would have left the church, become Episcopalian ministers, married and then gone back. I know some who would have in a heart beat.
I don't think that a person in that senario can become a Catholic priest. If you were previously Catholic and then converted to Episcopalianism to become a minister, I don't think the Vatican willl allow you to be ordained as a Priest.