It can be done. To bring the headers over the top just remove the A/C, coolant expansion tank, steering shaft and power steering pump. Then when you dive under to return the exhaust to the rear simply remove the oil filter and lines and since there's no A/C you won't have to worry about those lines. If you don't like that scenario, you could opt to keep the "accessories" and use 3/4 inch primaries and a 1&1/2 inch exhaust.
Obviously, I'm kidding about removing all that stuff but they will all, at the very least, need to be redesigned or moved to other locations. This is one reason why Axis engineered my system to go below. The other was heat and its proximity to the hood over the long haul, especially if there's to be any time trials, driver's ed, road racing, or anything more than just short bursts of fun. I must admit, if you want to show your wares there's nothing more ballsy than a pair of turbos crowning the engine compartment.