Below is an excerpt from my thread about building the Italeri HEMTT LHS. I hope this helps. On the various models of the HEMTT the front four tires ARE DIFFERENT from the rear four tires.On the Italeri model
(I can't speak for the Trumpeter kit.) the front four wheel drums are different than the rear four. Special care should be taken to insure that the correct drums are used in the correct locations. However there is nothing about the model that prevents you from putting the wheel drums on incorrectly! The most visible difference between the front and rear wheedl drums is that the wheel center housing projects out further on the rear wheel drums than it does on the front four drums.
As with most REAL wheel drums, the center of the drum is off-set relative to the centerline of the tire tread. With the HEMTT the off-set wheel drum can be mounted on the vehicle facing either way. Due to the presence of the steering mechanism on the first two axles the off-set of the wheel drum is to the outside to allow more space behind the wheel.
On the rear two axles the axles are actually narrower (no steering mechanism) so the off-set of the wheel drum faces the inside. Doing this keeps the finished tread width of all four axles approximately the same.
The same is true for almost any heavy truck.
As per the Italeri instruction sheet the front wheel drums are identified as parts 2G. The rear wheel drums are identified as parts 1G. Finally the wheel drum for the spare is identified as part 3G and has no wheel center at all.

. . . . . . . . . . . FRONT WHEEL DRUM . . . . . . . . . . . . . . . . . . . . . . . . . REAR WHEEL DRUM . . . . . . . . . .
. . . . . . . . . OUTWARD FACING OFF-SET . . . . . . . . . . . . . . . . . . . . . INWARD FACING OFF-SET . . . . . . . .
. . . . . . . . . . . LOW WHEEL CENTER . . . . . . . . . . . . . . . . . . . . . . . . . HIGH WHEEL CENTER . . . . . . . . .