Lunati 268 Cam
The guide down, where the seal sits. With that much lift the retainer will hit the guide seal, or even the guide itself.
New shafts, sure.... It's your call if you want to use your old stock ones if they are in good shape, I sure do, but most think I do things wrong.
If they aren't ridged, and wore, why not????
Cost?
IDK, COMP pushrods, if you can wade through the BS getting the RIGHT ones with them, are like 90 bucks, ISKY lists the correct ones, but they are like 180... Not worth the price, unless you just want to order them and be done with it.
The outside of ball to outside of cup measurement you will need, is around 7.250. ISKY lists 7.265, I actually gave up on COMP sending the me mech 2.500 pushrods twice, and ordered a mech ISKY cam. LOL. Screw hyd lifters, I hate them anyway.