the hughes 1199 spring/retainer/lock kit will get you there as far as lift and not machining the spring pocket. however, above .500 lift is where you run into problems on the magnum heads with guide to retainer clearance.
*sometimes* you're in the clear, sometimes not but with .555 lift i'd doubt it, so absolutely check and adjust as necessary. personally, i'd have a machine shop undertake the work.
the rockers *might* need some clearance ground on the inside to clear the top of the spring/retainer. but i'd call that a perfect excuse to upgrade to roller rockers...