More power from my 360 Duster?

You may want to re-think the cam. To run dual springs you need to cut the springs seats in the heads, trim the guides to run teflon seals, and replace teh retainers and locks you currently have. I would sugest the XE268 Comp, which can use a sinlge spring witha dampner... That fits everything you have now, and they do similar jobs.