Exhaust

I need some help!! I have a set of GT40 heads that were rebuilt, ported and polished and bolted onto my 302 stock block. For a 1989 Mustang GT, I bought a set of BBK long tubes and installed them on the heads. However, once I ran the car, I have experience leaks on the header flange. Basically they don't fit right on these heads. Which set of long tube header will bolt onto the GT40 heads? I have added some photo's so you can see my dilemma. Any assistance would be greatly appreciated.
 

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I have GT40X heads and the ones that port-matched the best for me was the JBA Cat4ward shorties. I had bbk equal length, same 1 5/8" tube, but the ports were much smaller. BBK fit fine on the stock heads.

I briefly looked and the best I could find was this one for the p-heads. - Kooks Headers 10102200. But, Its 1 3/4" tubes with a 3" outlet. Still dont know how well it would port match.

Whatever headers you get have to be for the GT 40-p heads.
 
I had the same problem as him but reverse with the bbk equal length shorties. My head ports were much larger than the ones on the headers.

Maybe its a manufacturing thing? Not sure.