Well you definitely need a tubing bender and if you have a nice stainless Down pipe most people want it tig welded. But the Down pipe doesnt have to be tig welded really unless its right at the turbo. In this case you would just be extending the area just after the bend. You can Mig weld that if you want, but you would have to coat it with some VHT high temp paint and heat wrap the down pipe. The would help prevent the Mig welds from cracking at the down pipe and heat wrap would hide everything.
Anyways kids, I got an adapter made today and the Jig is just about complete. All i gotta do is drill locating holes and itll be ready to mass produce.