To remove the body from the HO RS-3, work from the underside.  First remove the couplers by unscrewing the coupler covers at each end, removing the screws, and then removing the coupler covers and couplers.

Then, remove the one screw holding on the fuel tank cover.  That will uncover two more screws.  Those are the ones that attach the body to the frame.  Remove them, and the body will slide right off.

-- Steve