I'll be blunt... the only set of Schubecks I trust are the ones I've had since 1999. Mine have 6000+ miles of street / strip / dyno use on five different cams w/o any issues. However, something happened w/ their quality control or manufacturing process at some point after I bought mine and they shipped a lot of lifters that simply didn't hold up before going out of business.

If you don't know when the set you have were made and they haven't ever been used, I'd be scared to put 'em in anything.