We had a 15 series in our "new" house built in 1966. It did have an adjustable upper rack, if you looked closely. At each place where the upper rack attached to the 2 rails, there were three places in the side of the rack that could sit in the hook of the rail. The rack could go up or down or sit at an angle. When we finally moved mom out of the house in June, 2003, the machine was still going. Granted, it needed hotter water than today's machines, but it was still a very good dishwasher.
I like the KDS-18 with a water source under each rack. I bought my first one in 1977. When the 19 series came out with the longer upper arm, I installed the longer arm and bigger China Guard. It is still washing and drying just great as is the second modified KDS-18 in the kitchen. I also like the Constant Rinse sprayer at the top of the tank. I had a 21 and 22 without it and that was just one more thing that I did not like about both machines.
The KSD-14P downstairs is a great performer, but now is mostly used to clean up after candy making. The KD-2P original top loading portable actually holds more than the last TL portable which my mom has in her apartment. As far as we know, the KD-2P was the only double-walled portable that was all porcelain, outside as well as inside. The tub has much more vertical height than the front loading KAs of the time and, depending on which, or how many, of the three sections of the top rack you wish to remove, it will easily accommodate most anything that I want to put in it.