you can do anything you want. cases are cast at the foundry in the same mold. upper and lower have matching numbers engraved . rear motor mount. right side. using unmatched cases can cause premature crank bearing wear.
i got a crank, stems, front shock, a arms, swingarms, skids, bumpers. FREE OF CHARGE. COME N GET EM.
LOADS OF SHIT IN MY JUNK PILE. a crank would make a cool lamp.
i have 3 a arm frames 2 fresh powdercoat. one black, one black chrome. 1 bare. cheaper and more efficient to buy a frame and get upper a arms. i have those also. call john 215 880 1990.