Talk to Mike and ask him to give you the contact to the manufacturer of the system. Originally I wanted duals but after talking with the shop we (the shop owner and I) decided a single would be better because the tunnel in a round body drop top is very narrow. After a few conversations, we couldn't imagine how dual pipes could fit in the tunnel with the body brace, transmission mount, tranny and driveshaft in place.
When I got my system, the shop didn't have a dual system for a round body drop top fabed up at that time. He was looking for one to fab up a system. I ended up e-mailing a number of photos with measurements of the underbody of the car to the shop and reviewed the space that he needed to fit the cross pipes. If you really want one, I'd check with them if they actually fitted one before buying it and having it shipped. Of course, another method is to look at having the shop alter the system to have duals after the axle. I'd imagine they would either need two mufflers - one on each side of the gas tank - or relocate the muffler to under the floor somewhere. Keep in mind that I didn't have a bolt on experience and some creative fabrication was required but I eventually got everything to fit. Hopefully yours will go much smoother.