Yes, I kind of had the same issue with my summit shortys. So I took a ball pin hammer, and smashed the flanges upword so that I could use donut gaskets. Then I went to autozone and got some steel donut gaskets ( after tring some different fiber ones) and made that fit the smashed up flange. I made like a cup for the donut gaskets to fit into. I got some 3/8 grade 8 bolts and nuts so that I could tighten the hell out of it all. The donut gaskets fit the exhaust pipe flange perfectly, and I tried my best to copy that on the header side. I did all of this on the truck. It will be much easier to do before the install. Once I got the flange on the header close to what is on the exhaust pipe, I installed the donut gaskets tri flange, and bolts. I tightened the hell out of everything. I had to fight with it some to get it to seal, but its been all good ever since. Thats been 6 or 7 years I guess. Also before you do anything else, strip off the paint, and paint them with some VHT header paint. I did mine when I installed my headers. They still dont have any rust after all of these years. Just follow the directions on the can. When you get the steel donut gaskets, ask for steel donut gaskets for a 1972 c-10 with a 350, and get 3 so that you can use one as a template. That way, if you mess it up bending the flange on the header, it wont matter here are mine installed.
