You just might have to get a hand. Increase the lengths of the wrenches by welding on extensions or perhaps a couple of short pipe lengths might help as well. Since you quote you cannot get the appropiate feeler gauges in they do need done as you are aware. They are also snugged together pretty well to perform as a jam nut assembley. If you increase leverage make sure the wrenches are a good fit as you do not want to round anything off.