RE: Custom Made 1/5 Monster truck
GWS have a new 1/4 - 1/3 scale servo on the market. They are well priced & at 6V have 28kg of torque. I think the part # is GWS 666.
Have you thought about titanium for the frame? Strong, light, can be tig welded & if you get really excited, you can annodise it.
Sounds like a great project.
Good luck.
Paul.