They were just about unheard of for general farm use in our parts. The ones I remember had custom mounted front pumps and were very crude. That front axle pin was a weak point so they had small buckets. The one arm Ford loaders were the quick hitch of their day and more common for farm use. It may be just about as cheap and a lot easier to find an old tractor with a mounted FEL. I saw a decent looking 30 MF with a factory loader for about $1800 a few months ago.
We wound up getting a backhoe to get a loader because we could not find much for less than $5K for our 1976 265 MF. During this process I have learned it is next to impossible to buy a used loader for an old tractor and new ones cost more than older good ones already mounted to a working tractor.