You'd need the 212(h) waiver for sure as there are no statute of limitations in US immigration laws, so even a 50 yrs old conviction would cause road bumps.
Path to this waiver would partially depend on your (USC's) personal situation if you could show your hubby being away would cause extreme hardship on you. Or else he could apply on the basis that more than 15 years have passed since conviction - this would heavily depend on his post conviction rehab/character development.
One thing you/he could do before going for waiver is to check if in the country where conviction occured, are there ways to get the conviction expunged/sealed off/set aside etc? While this would not remove the conviction for immigration purpose, it would count as a BIG rehab factor.