Your caption with the A&M 86' hi-cube brings up a truth that most really don't understand... there is "ANOTHER" version of these long cars, called "appliance" or "paper" cars, that exist and they see considerably more use and more varied use than the autoparts cars of the same or similar design.
These cars tend to be around 100T in load limit since things like appliances and rolls of paper (go ahead, pick your type) are considerably heavier than what the autoparts ladening is and can be seen over a number of different lines, especially so where a corrugated box plant might be located. Such cars show up on branchlines having furniture plants that build case goods (end tables, coffee tables, dining table sets, bedroom sets, etc.) as well, making them very valuable in a number of ways.
One of the last memories I have of the Carolina & Northwestern's operations between Hickory and Lenoir, N.C. is of a Southern GP38-2 hauling one of these monster boxcars from Lenoir to Hickory for forwarding to wherever, the only car running behind the engine and that on a day that the train typically did not run. Furniture was already on its way out as far as rail shipments went on the line, which made this particular car load even more special.
I applaud your efforts to provide us with unique and unusual cars... it is greatly appreciated!!!