The only walker that will fit in the res spot is #12616 for the aluminized and #14616 for stainless steel. Then go staight out the back. If it's too loud get some res tips. I was inches from doing this myself till a good group buy came along for cat back.
Mr. Chris Wong from CTA motorsports is to thank for the trial and error on this one. Give him a call or email for more specifics.
