GT200 on a GT engine case requires one gasket.
GT240 on a GT engine case requires one gasket. No packing plates are required for the GT240 as the cylinder is made to the correct length for the 62mm stroke.
GT 250 on a GT engine case may require either one or two base gaskets along with a 1mm base packer to allow for its 64mm stroke.
GT kits on other engine cases may require from non to three base gaskets.