New roller cam...

lobe placement is critical. They need to be of center to spin the lifter. Always check all lobes. Truing the lifter bores is a must on 50 year old engines. A worn bore can misplace the lifter.

Never assume they were placed correctly from the factory. The more lift you have the more critical it is to be correct.

Roller cams are more forgiving. But to much movement can break the roller. Once those pieces go through the engine you'll need more then a new cam.

Always check the lifter bores. Many Machine shops just drop the lifters in and always blame it on the Cam manufacture when they fail. Also if bushing the bores to true them install stepped bushings so they never drop. My son cuts his own. He buys blanks.