The item under consideration is a Mechanics Crane Bed (Model Number IMT 3016), which is a part of a telescoping crane truck. You state that the article was made in the United States and is being imported from Canada in used condition. It consists of a full truck bed frame with a crane attached to it. The crane is not fully operational until a hydraulic pump, which is mounted on the truck, is installed.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N322219