Most of my chassis parts were bought from Northern Tool.
Here's the link to their kart pages.
It's mostly fun-kart parts, cheaper than real, engineered kart parts,
but handle the lighter duty tasks of a scale chassis pretty well.
Here's a shot of the underside of the chassis. This winter, I'm adding rear
suspension, as it hops too much for my taste, when it encounters larger
bumps in the track surface.
The chain has now been replaced with a v-drive belt, as the chain was too
noisy and hard to guide over such a long run.