Here are some of the vehicles I converted or built by putting diecast bodies on Streets vehciles - incidently you want to use diecast, not plastic - you need the weight to keep the center pickups down.
-----These four cars first are all conversions of the "vintage truck" chassis, which had the smallest wheels of the various types of Superstreets vehicles K-Line by Lionel offered - those wheels were just about scale car-tire size. In every case I had to cut the stock chassis and adjust its length, epoxying it back together at a different length, something we would avoid with a telescoping chassis. The two at the top - '50 Chevy cab and Buick, are my favorites. The '57 Chevy at the bottom is my first conversion, in which I accidently epoxied the front axle solid (the wheels do not roll). It is a great runner, the wheels just slide along and when it is running you can't tell they are not rolling. These are stock chassis otherwise so they run no better than standard 'Streets vehicles, meaning too fast for scale city driving and subject to occasional stutters due to having so little contact surface with the rails.
The truck at the top is the first conversion in which I lengthened the chassis, using the vintage truck again. Lengthening a chassis is fraught with potential problems - too long and the vehicle will not go around corners well, but this guy is just barely okay even on 16" curves, although he slows a lot. Again stock drive otherwise.
The race car transporter at the bottom is a converted stock wheelbase UPS delivery step van chassis, with bigger wheels than the vintage truck they look better on a big vehicle. I also used that chassis for the two buses farther below: on all three, I repowered them with massive (from full size diesel locos) flywheel motors with 3:1 reduction gearing so they run much better (they all still go 65-70 mph scale which is plenty but will creep at 5 mph smoothly through town).
Top, my city buses. Bottom, completely scratch built (except for the wheels) 18 wheeler.
