[Kube]

On the other hand, IF more restrictions are placed on our old Fords, a catalytic converter may be the easiest and most reasonable method to get within whatever standards may be applied.
A converter typically does the most to reduce emissions of any of the numerous systems on our modern vehicles.
The problem I see applying one to our old Ford is not the fit. Heck, any "generic" converter could be made to fit rather easily. Nope, what I see as the major issue is how long the life of the converter would be.
Our Fords are not very efficient and as such no doubt pump out a lot of "yech" through the exhaust. That "yech" would quickly clog a converter.
Ever near a car that smelled like rotten eggs? That's too much unburned fuel getting to the converter. That in itself is a clear sign that particular vehicle is running poorly. Subsequently, the converter "fills up" and fails prematurely.