Dave,
I just returned from a quick trip to Montrose and had a chance to investigate the car I believed to be the 5510.Seems as if we were both wrong, it is neither the 5510, nor the 5610. I found a very faint number on the inside of the end door. Faint, but clear enough to read the number. 5710. After examing the remaining paint on the outside, 5710 seems to fit there, as well. I'm convinced. I sent my photo's to Vic, he agrees with the 5710 conclusion.I will send them to you as well, if you'd like.
As a side note, if you'd care to update your excellent list, the two burned cars were the 5615, and the 5821.
Doug