The original version of the MOC had wheels mounted a bit wide for the width of the cab. The version published here uses a different steering rack to reduce front wheel width by one stud, different differential to reduce rear width by two studs, has a roof one stud higher, and the front hood panel one stud wider.
These types of files are created with the LDraw system of software. You will need to install compatible software to open and view the instructions.
A full list of available software is on the LDraw site.
This MOC also has a LEGO Digital Designer file available: 3D Model