Most WC-1 motors use a 14 MM spark plug, whereas the NE motors use the 10 MM spark plug. The later WC-1 motors used the same 10 MM plug as the NE motor. If I were you I wouldn't worry about spark plugs, but would try to find the parts to upgrade the motor. The best way to upgrade is either buy the NE upgrade kit, or obtain only the necessary parts. It is possible to make the motor "bullet proof" by only changing the cylinder, head, head gasket, head bolts, and exhaust manifold. You can keep the original carburetor, and use the original piston & rings. The kit has the same parts, but includes a carburetor, piston & rings.