What flange is warped?  Around the exhaust port on the head or the exhaust
pipe?  If it is on the pipe why not just buy a new pipe (way cheaper than
$200).  Or you can go the ultimate cheapy way and use a new gasket and some
furnace cement to fill in the irregularity of the flange (done it on old
Catalytic convertors which seem to not want to seal properly even with new
gaskets).  The cement is good to 5000 degrees. And will hold the system
pressure.
Prices for new pipes can be found on my website.
Hope this helps,
Ken Wilford
http://www.vanagain.com
John 3:16
Office (856)-765-1583
Shop (856)-327-0027
Fax   (856)-327-2242