For the guys who have headers on their 401/425 Skylarks with nailheads did you have any fit issues and what brand/vendor's are you using? How about exhaust pipe size. It seems that 2.5" piping can very often cause resonance that is very annoying. Considering 2.5" to the mufflers and 2.25" for tailpipes. Any experience with either of these, headers and/or piping? THX, mark