I posted details about these in the Scratch builders section. Brass and Lego chassis. The bodies are resin cast ones I made myself. I made up a master using a Scalextics Lotus 49. The tube is kind of generic, and then just scratchbuild the rear housings and modify each shell to better represent the prototype I am modeling. I bought the front axles assemblies( lotus 49) and use the same thing on each build. These cars are all powered by the small Minebea S cans, but they move right along, and are built to race against each other, so having them the same makes it fair.
Here is what the chassis looks like
I fashioned the rear springs out of wire and styrene. The radius arms are made out of elastic thread. They are very forgiving to shocks and this technique works very well for a slot car. You will notice that the inserts on the rear wheels are made from snap fasteners from the fabric store. Since these pictures were taken I have modified these and drilled out the center. The front rims on the Ferrari represent how these look. The BRM is the lastest car I built and each car has gotten slightly better then the last as I developed new techniques.
I want to do a Lotus 33, but right now I started work on a Ferrari 350 Can Am car. Just made a mold of the master, so I can now cast some Ferrari Can Am cars. They weren't successful on the track but they sure looked pretty.
Thanks for the comments