OEM magnum lifters setup

Whaaa? The lifters spin in their bores due to the crown on the cam lobe....

Not on a Magnum engine. They use hydraulic rollers. The factory ones have a paint mark on them to note which "side is up". Aftermarket ones, or most used ones there is no outward mark except for the hole itself.

If the cam and lifters were changed and replaced with a flat tappet I apologize - that wasnt how I read it.