Re: 5ft. Trophy!
Sounds like you put up a good fight and was compitive.
For header gaskets, I use to soak them in water over night before installing them, old time trick, works, but now I use a high temp RTV, red,copper or black.
I prefer the copper stuff. And tighten the bolts every day for a few days until they have set in. Use the RTV just on the header side of the gasket.
If your headers have the solid flange that runs the whole length of the head, and it seems warped, cut the flange between the first and second pipe as well as between the third and fourth pipe. This may make it harder to start the bolts, but will allow it to flatten out when you tighten the bolts.