As I thought, it's a truck rather than a car... but high-stacked usually refers to the load it's carrying in the truck bed behind the cab -- although it might be the level of the truck bed from the ground (higher rather than lower). But these are just guesses -- I'm afraid I'll have to leave it to some pickup truckers to fine-tune this answer.
High-stacked may refer to the vertical exhaust pipes (or extensions) on trucks that are often called "stacks". The exhaust extensions may be very tall to raise the exhaust above the trailer which is often taller than the cab of the truck.
Something about this is not right. Does Dodge make truck cabs? Not in recent decades, if ever, as far as I can recall. They make pickup trucks for sure, but these do not have high or low vertical exhaust systems.