Truck frieght is all about classes, cheaper say if you are shipping a used engine core for rebuilding, vs say a build hot rod motor, sure you can class it leesser but it it get damged, then you're screwed, they are not goping to p[ay you $5K for used motor. Shioiping a Spridget tranny (60 pounds), and A series engine (275-300 pounds) are tow entirely different things. For exmple someoen sending mea core engine to rebuild can send it to me any ole way, laying on it's side strapped down with tie downs, but I have to send back with lot more care, I build a set of brackets to bolt the engine to the pallet, I get $125 to pallet a motor to prepare for shipping, it's a half a day project, but you have to get the engine there in good shape.
Oh, also there are other liittle catches, say you don't have loading dock, or you need it delivered to your house, I do terminal to terminal most times, so you go to the nearest terminla and pick up with a pick up truck.