Riketsu,
I had the same problem with a 41617/41616 Novarossi header and the 353 motor. To solve the problem I used a Dremel to grind about a mm or two off the belt tensioner carbon fiber plate (around the header area); just enough to avoid header/tensioner plate contact. The mod is working fine for me (it did not weakened the belt tensioner plate). I hope this helps.