I didn't fab this up , a friend of mine welded it for me Yesterday, the back story on this head pipe is I bought it knowing it needed repairs. it had a small hole on the inside of the pipe, I decided to see if I could find it, so with a small drill bit I began drilling holes on the outside of the pipe where i thought the hole would be on the inside, I took about ten holes to find it but I finally got it to drill through the inside hole. When I was drilling I drilled through something rather soft, someone had done a prior repair on the head pipe with JB weld and repainted it.
I took it to my tig guy and he said no problem, I knew he would need a fairly large hole to get the tig torch in there so we used a hole saw without a pilot bit and a drill press to drill out all the nastiness, then he welded up the inside hole and I told him to just weld a plate up on the outside instead of trying to make a perfect size circular disc to weld into the hole, time equals money and I don't plan to sell this exhaust system anytime soon, he had it ready to pick up yesterday afternoon.
The really good part is he used to teach welding at the local high school and he offered to teach me how to tig weld, I have a tig setup at my shop but I never got a bottle of argon and a regulator to set it up, I also need to check the gas and water flow solenoids because it has a water cooled torch on it. Hopefully by early next year I can get it all set up to tig my own stuff.