Try an impact gun with the standard 17mm deep well socket, or perhaps a rubber strap wrench on the standard 17mm deep well socket with the shock socket inserted inside. Sears sells a 1/2" drive electric impact gun that may work nicely (use it to loosen the shock nuts and return it). Now I understand why you wanted a 17mm spark plug wrench ... as it has a hex head that you can hold/turn with an open end or adjustable wrench.

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Fred Hoelzle