bbk headers w mac pro chambers?

Any competent muffler shop should be able to help you out

I have BBK 1-5/8" longtubes and a MAC prochamber that I ordered specifically for longtubes. It didn't match up very well-- as in not at all. Unfortunately, that's the nature of the beast when it comes to exhaust parts from different manufacturers. As mentioned earlier, any exhaust shop will make it work. My shop bent up some pipe and flanges and made it work in about an hour.