The chassis can be thought of as the ‘structural skeleton’ for the truck. It is the platform that the rest of the truck is laid on and contains the axles, engine, cab, fuel tank and batteries.
The chassis has the greatest effect on the size and shape of the truck and is crucial to fuel economy—a truck much larger than you need will waste fuel. A chassis which is too small increases the chances of overloading or could create the need for extra trips and expense.
The size and weight of your intended loads will determine the axle placements, as expressed by the wheel arc (distance between the wheel axles) and rear overhang (distance between the back axle and the back of the truck). As these have a direct effect on the type of body that can be fitted to your truck and the loads it can carry, make sure you spend time with your tax dealer to ensure they are right.
Make sure that your truck design allows for proper load distribution. You run the risk of overloading the front axle of your vehicle if you carry too heavy a load on a truck with a short wheel arc.
If the wheel arc is wrong, you won't be able to carry as much load as the same truck with the correct wheel arc.