Review, pictures, instructions : https://www.nico71.fr/western-star-6900-twinsteer/
Video (final presentation) : https://www.youtube.com/watch?v=mfNE-GMKvX4

Rebrickable link :
Trucks (instructions for sale): https://rebrickable.com/mocs/MOC-117722/Nico71/western-star-6900-twinsteer/#parts
MudPump (free) : https://rebrickable.com/mocs/MOC-117726/Nico71/diesel-mud-pump/#parts

Design process :
How I designed the Chassis : https://www.youtube.com/watch?v=XuewxjBygss
How I designed the Bodywork : https://www.youtube.com/watch?v=0xgCmiPqv2w