I have to replace a manifold gasket and have a set of these laying around... Worth bolting them instead of the 99 ones? Would they even fit? I don't plan to install headers anytime soon.
They will fit but will not be worth anything power wise. The only difference is that the 03/04 ports are more elliptical IIRC. I posted a picture comparing the two years ago. Not worth the time or effort. Just get your seating surface as clean as you can and slide the new gasket in there.