If you are using a reground cam, this is not too uncommon. The smaller base circle will lower the lifter in the lifter hole, and the rocker nuts can bottom on the stud. Keep in mind that there are also three different rocker stud types, some have an undercut shank and will allow for a lower adjustment.
I've used 7/16" hardened washers as shims in the cases where a reground cam used up all the available threads on the rocker studs (with polylocks and with the 2.8 Chevy locknuts).
Bob