...I'd start with a 8-12" section of 2 1/2 or 3" o.d. tubing and place a 20-30 degree bend at the half way mark (middle)... angle cut one end 2-4" from the center and leave about 3-4" on the other end from center and fit em up from there... or you can go to the local exhaust fabrication shop and have 'em do it for you.
I just happen to work at one...
