I was in my 18th year when the KCS cars came on line, along with the PRR lightweights, the FEC, EL, and B&O observations. There was a yellow UP diner in the mix, and a bunch of NH stainless cars. It made for terrific train pictures, but it sadly sounded the death knell for the heavyweight parlor cars.
I always loved the C420's. They were great looking locomotives and the "swoosh" World's Fair paint scheme looked great. When the MTA locos arrived in pastel colors we got a few slides, but once the World's Fair scheme began to disappear, the pastels were repainted as well.
It was about that time we younger railfans started chasing anything non-MTA. The M1's were about as interesting as mayonaisse, but we shot those as well. I still can't believe those new M1's are all gone.