OK, I'll start reposting the construction photos here. This shows the basic Kato 11-103 or 11-104 chassis filed down to the basic elements. The Bachman greyhound bus tire (which normally is way oversize for anything) is on the left, and it is filed down thinner. The difference between the stock Kato 42" wheel and the 11-105 27" wheel is shown at right, yes, it really does make that much difference.
This shows how really simple the start is; three pieces of styrene, one for the deck and two sides, and then the truck tires glued on: