well you can check the obvious things like looking at them but it will be hard to tell.

To be honest, the only way the top end can tap, is if there is gaps.

If you spin the engine over in the same manner as you would to check valve clearnces using the rule of 9, you can play with each rocker and see if there is any noticeable play, if there is that indicates wear, if its tight and no slop then that should be a good indication there is no wear

you did say you fitted a brand new cam and set of lifters didnt you?