Without having the tires mounted on the wheels, and on the truck, it would be extremely difficult to calculate. Hub offset, wheel hub depth, steering angle lock-to-lock. How good are you in 3D geometric calculations? Do you have an engineering buddy with AutoCAD?
For simple measurements, you can use the overall tire/wheel values to produce width and height.
295/70/18 equates to 295mm wide, 70% of the width is the sidewall height, and the wheel is 18". Why they mix metric and SAE I'll never know. Therefore...
295mm = 11.6" wide, 70% of that is 8.1" sidewall height, 18" wheel size. The overall height of that tire/wheel combination would be 8.1" + 8.1" + 18" = 34.2"
You should be able to figure the other sizes out on your own.
Sounds like a hybrid... most likely 33" tall, 12.5" wide, 18" wheel.