anything i need to know befor doing this
im installing 496 aluminum exhaust on my 454 trs

Yes, go to the hardware store and get a couple long automotive style studs the same size as your manifold bolts. Install the studs loosely so that you can slide the manifold over the studs which will hold the manifold and gasket in place while you tighten the rest of the bolts. Then you can remove the studs and install the last 2 bolts. You also are going to want to use some good (silver) anti-seize.