No problem with a new lifter on an old cam... but
, you absolutely have to put plenty of that cam lube break-in goop on the lifter and cam lobe so that they can wear-mate... or they'll be eaten alive!
Also, the noise can easily be an adjustment issue, and since you did not say that you SAW a bad cam lobe or
a bad lifter bottom, you might still be able to adjust it out?
Just sayin', but you hafta go with the simplest, easiest first before you go disassembin' and replacin'! Just sayin'!!!