So my knee jerk reaction is, if it’s from eBay, send it back not as described, given the box doesn’t match the item.
If you got it for a steal of a deal, or it was the last suffix number to “collect em all” then it’s easily returned to 3 rail by buying a set of atlas 3 rail Bettendorf trucks. If there’s no good reason to keep it, or if the car is easy to find, don’t even mess with it.
The 2 rail trucks can be resold, but the coupler boxes are prolly gonna get sacrificed in the process of removing them. Since you don’t need them, it’s more important to not mangle up the end platform. On the back side of the coupler box, there is a loop that the box lid is snapped into. Cut the loop off. That will free the tan on the box lid. Once the lid is off, slide out the coupler and spring, then you can unscrew the box from the car. If you fight with the snap tab to get it off, you’ll probably end up busting something off the car. It’s just not worth the effort.