people think they wear over time, but what wears is the seat. also the valves after heat cycles and such grow... so mostly u will find exhaust are fine, and intakes will tighten up over time.
in book there is chart. u find ur clearance measurement, and pad u are using, then it will tell u which pad to try. best thing u can.. is take them out, and keep notebook ( i use service manual and keep tabs on them) write down and draw out the valves and label them, then put what size shim is in each vavle. next time u need to adjust them.. u open to that page, see u have say 185 shim in it, then u know whats there, u dont have to take it out, then go get shim...u know what in it and u can figure out what u need without pulling cams out yet. just saves some time.
also dont go by whats written on pag. get set of calipers or mic's and check them. they can have some wear on them as well. harbor freight sells digital calipers for like $14. good to check , even new one..so u can tell if its correct size.