Ran into the same issue with the same headers. What a PITA ! Many emails and telcons got me no where !!!!!! Send them back and get headers made for a 351W. Hooker swore to me that these are for a 289,302,351w. When I explained that the 351W was 1" taller therby driving the collectors into the floor boards, they offered to allow me to ship them back to them to test fit on their fixture to see if they are made correctly. If they fit their fixture then I would have to pay for the return ship cost. Never once did they acknowledge the 351W being taller by 1" !!!!!!!!!!!!! I already had $500 inot this and just at the end of my rope when i did MORE resaearch and found loads of peep saying the same thing. Hooker is not in the business of correcting this issue is what I have concluded. SO, I will not buy from them again. I went with Dougs midlength headers D669Y and there where no issues. Yeah it cost me more time and $ but I will not do business with a company that denies having an issue with their high :mad:$ product.