If I can set the base of the lifter on a flat piece of glass and feel a very slight rocking...would it be ok to use it on a new cam without resurfacing the lifter?
Are you willing to bet the life of an almost impossible to obtain new cam on running used lifters on the lobes? That's a gamble I'm not willing to take. Drawing to an inside straight in a poker game only has 32:1 odds against being successful, and that's probably a safer bet.
Jerry