I'm putting a set of Vortec heads on my sbc 400 my cam has a lift of .443/.465. i've heard a lot of different things about the highest lift vortecs can take without machining ive heard .420-.550. which seems a little high. I have matching springs, Competition Cams 742-16 Steel Retainers, with locks, do not have new valve stem seals yet. I'm wondering if with what i have if i can use this cam with theses heads without cutting the valve guides down. any help would be greatly appreciated.