Deputy,
Just a heads up on the 682's. A dealer (store) in Northern NJ (now out of business) REGULARLY had his mechanic take 681's and add the linkage to make them 682's. They also apparently had the rubber stamps to renumber them. It was almost impossible to tell that they had been modified. It was perfect work to keep the mechanic busy during the summer doldrums.
I don't know how many in total that they made, but I would guess in the dozens at least. Back in the late 80's early 90's it was very hard to sell a 681 for a decent price and 682's were very hard to come by. This dealer magically always had one or two on his shelf. As soon as one would sell, another one magically appeared.
This is the same dealer who got caught selling a bunch of stolen trains (MINE). Anyway, just a heads up on the 682's. You may want to ask a lot of questions from a seller when you come across one. Real ones really are not common.
LionelFlyer