A local exhaust shop could fab you up the pipe pretty cheap I think. I bought the ATS with the larger outlet (not the housing, just the elbow. There is actually a replacement center section that doubles the price) and downpipe for somewhere around $280 after taxes and shipping. If you can avoid using the ATS downpipe, I recommend going with hypermax or Banks. The ATS uses a "slip fit' design that doesn't work worth a damn. Some guys have not had any problems with theirs, but most will tell you that it is garbage.
Just to clarify, the 3" downpipe is a worthwhile improvement, just not a slip fit style.
Good luck, I hope it helps.