33C

Cardboard is a great material for the larger scales. Check out some of my "cheapo" models. With diesels, I would have 2 or 3 layers to the bodysides, to give relief, by cutting out grills, doors etc. The roof dome can be shaped balsa wood. Check out Amazon for the cheap, electric motor and gear sets they do. Enough for 2/3 models for sub £10. Also, look for speed controllers for the batteries at about a fiver each. Looking good so far!

Have you thought about using Micro-Scalextric car chassis, like a small Black beetle but a low floor pan. Just change the wheels. Pick up could use the braids rubbing on the rear of the flange......