As a rule, if the cam is worn badly, they will tap, because of the wear and the fact the followers can't take up the clearance in the valve train.

Some people say they have seen worn cams that don't tap.........i myself i can't see it though.

Has the car had a performance shaft at any time?

If you look on http://www.pumaracing.co.uk/cvh.htm its got quite a lot of info on the top end