I started hunting in the mid 50's and back then (and before) full choked shotguns were the norm, as well as longer (28"-32") barrels. A person generally owned one shotgun that was used for everything, including waterfowl and upland birds. With early powders it was believed that a longer barrel was required to fully burn all the powder. Over the years shells were improved and loaded with faster burning powders, thus the longer barrel was not needed. However, there are those that do prefer the longer sighting plane, especially for pass shooting waterfowl. With new plastic hulls and wads shot columns held together better and that made it possible to get tigher patterns with a more open choke. Then came the era of steel shot. Since steel shot did not compress or deform like lead when it passed through the choke area of the barrel, shooting a lot of steel in an older full choked gun would damage the barrel. Thus the need for more open chokes.
I'm sure that a lot of these older 12 ga. guns are also chambered for 2 3/4" shells and not 3". Back when I was a young hunter I didn't know of anyone that had a 3" gun. Not sure you could even buy shells at the local Coast-to-Coast.
There is nothing wrong with some of these older guns, it's just that everyone wants a 3" or 3 1/2" gun with choke tubes. There are usually some good buys to be had on these shotguns because there is not much demand for them. If a 2 3/4" gun will work for your needs you could do a couple of things with it to shoot steel. You could have the choke bored out to Modified or IC. Or you could have choke tubes installed. And if you are having choke tubes installed it would also allow you to shorten the barrel to the desired length.
Sorry for rambling. Hope this was the info you were looking for.