You would be better off just buying a set of works shocks instead of the used 660 shocks since they are valved and sprung for your weight specifically and also riding style. The shock swapping thing won't give you the full potential and it won't be much less than the works. You could also get rec series upper end shocks such as elkas for not much more. You probably don't need the axle unless jumping huge, just go with +2" arms and offset rear rims.