Spark plug cross reference from David Olesen
Thread size	Thread reach	SINO (Torch)	Bosch	ND	Champion	NGK	Autolite
14mm	12.7mm 1/2"	E5C  E6C  E7C  E5T  E6TC  E7TC   E7RTC	W8AC  W7AC  W4AC  W8BC  W7BC  W6BC WR6BC	W16FS-U W20FS-U W22FS-U W16FP-U W20FP-U W22FP-U W22FPR-U	L9G   L7   L5 L95YC    L92YC  L87YC  L82YC RL82YC	B5HS B6HS B7HS BP4HS BP5HS BP6HS BP7HS BPR7HS	425 275 4123