Nick: that is a whole motor that's getting old. With any motor, if you rev it higher with a new cam and heads combo you will be hastening the time until something fails. With a high mileage motor, that failure is likely to be sooner rather than later. That said, it's still unlikely that a lifter will be what fails.

Rich Krause

 

Thanx for the insight guys!
I know of a couple guys that used their stock lifters and never had problems. I just wanted to confirm