Miles really don't matter that much to me, just the motor condition. My 84 has 84k miles more on it than my 83, but the 84 doesn't burn hardly anything, where as the 83 I suspect burns a couple qts. per oil change. However after buying the 84, then the 83 I've decided no matter which car I get next (W124?) it will be a southern car. Everything on the 83 is rusted so it is hard to work on, while the 84 is almost a dream to work on.
I would also be concerned of the seals if a car was parked that much. Myself, I would also like having a turbo in my 300D.
Jeff M.