How bad did I #$&% my piston up?

Take your current bore size and multiply that number by the ring end gap factor they specify. In this case, for a NA engine the factor is .0065. If your current bore were 4.030", the top ring gap would need to be .026"

http://www.kb-silvolite.com/kb_car/clearance_pop.php

The ring end gap factor of .004 is typical for cast or forged pistons in a NA engine. If you're going to be using "power adders", the gap increases.