The Tamiya King Hauler is 14th scale, like every other production RC semi. Anything 1/10 is going to be custom.
There are smaller scales, but 14th is the biggest I have ever seen.
Welcome to RCT. Scaling a body up isn't hard. It's scaling them down that sucks because thin areas get too thin. Just use a 1/14 scale model scale it to 140%.