1/14 scale European Race Truck?

[Wombii]

This sounds like a fun project!
For the record, the tamiya race truck on a TT-01 sedan chassis you mentioned is 1/14 for the body. If you want a lightweight body to actually race, it looks like it could be adapted to the 1/14 chassis.
Looks like most of the racing trucks are based on the lower local distribution cabs, like Scania P vs Scania R long haul cab. Converting the Tamiya R to P is a pretty quick job, and it can be lowered another 6-7mm (1/4" ?)by turning the front chassis brace / cab mount upside down.