Magnum questions?

The lifters can be re used as long as the rollers are smooth on their OD, roll smoothly and pass a visual surface and cup inspection.
The factory Magnum heads can only go to about .500 max lift without cutting seats or using longer valves and matching springs.
My cam is .512 and I had to get the special retainers for it to go to that safely.
There is no way an uncut stock Magnum head is going to take .550 lift without longer stems and springs.