[RicksGTO]

Here's what I learned on mine. I would start with the tails to make sure they fit correctly, mount the mufflers in their clamps temporarily to detemine that they clear everything and that they exit at the tails correctly, all while making sure that the muffler inlets look to be on line with the line of the underbody, not tilted up, down, in or out or in a bad spot in the floor pans for clearance. This is where some people scratch their heads a lot as you will need to rotate the tails till you find the perfect angle to make it all line up. I even had to adjust (drill new holes) my mounting points for the muffler hangers to a different spot than the factory used to make the tails line up right. Once you have that done, then start on the other end and mount the downpipes and determine how they need to sit to pass thru the crossmember and gain the best ground clearance to line up with the underbody. From the mufflers in their spots and the headpipes in their's, you can figure how wide the front legs of the X need to be apart, then how wide the rear legs need to be apart to meet the muffler inlets. Those measurements will be important in making the cuts for it to line up well and for best ground clearance. Once you have those measurements, you can decide how far back to mount the X. From what I learned, further back is better, I'd shoot for 6" or more behind the u-joint. Only when you are sure it all lines up should you trim the pipes/headpipes for length and the legs of the X for width/length. On the hangers, there are not likely any mounting points between the front headpipe and muffler hangers but I am not as familiar with the large Pontiacs as the A and F bodies. There should be a rubber isolator between the body/frame and the hanger to prevent vibration from resonating into the body. On the rear frame to tailpipe hangers, Pypes has them with rubber isolators for most cars so check with them or you may be able to find a universal mount locally. On the welding, I would weld each joint except the front of the muffler connection. Use a stainless band clamp there to give you a easy point to drop the X to headpipes just in case you ever need to without cutting. You should not need any sealer in the headpipe to collector connection, just be sure the outer end of the head pipe flare isn't butting into the ears of the collector before the inner flared pipe is tight to the ball of the collector and you should be fine. Hope that helps, it's not really too hard, just measure twice and cut once!