Yes, you should have no worries fitting the plug door underframe to the single door car. I remember when I saw my first Kadee Micro-Trains car and marveled at how much better the decoration was than what I was used to. But THREE DOLLARS for a car?!? I was getting cars for 49 cents at Two Guys and Korvettes! If you think dating yourself by model trains is bad, consider popular music. If my dad were listening to records that were as old as what I play regularly, they would be wax cylinders...
Yes, I think about that quite often. The first LP's I bought in the mid sixties are 55 years old or older and 45's were 5 - 10 years before that. 55 years before then was 1900 - 1910! My oldest nine mm trains (Treble-O-Lectric) are from 1960 - 61 years ago. 61 years before that was 1899! Heck, the oldest Kadee cars are now going on 50 years old! Doug