These were hand built prototypes made from vacuum formed shells in white styrene over wood patterns in Marx model shop, one of many such projects that bit the dust when presented to the New Products Committee. The motor is a Hong Kong version of the Mabuchi ST020 as used in some HO cars in the day, and in the 1/40 scale Cox SuperScale cars. The body mounts are then machined from plastic stock, then epoxied, as well as accessories, to the body.
In some prototyping work, accessories can be actually injection molded in temporary aluminum molds, then vacuum plated. We used the process quite often at the Cox toy company, like on this 1974 prototype of the Datsun 240Z from the East African Safari race. The front lights are made from that process and added to the body. This and a Porsche RS sister car never made it to production.
We have similar sized Cox Mini Cucaracha (smaller than the Lil'Cuc) prototypes using the same motor and a stamped brass chassis that resembles the Cucaracha IFC chassis. Their size is similar to that of those Marx Indy cars.
Finding stuff like that is what makes collecting so much fun!
Lovely stuff even if, as Don points out, they are pretty ungainly...