For those considering an AirBar...you can fit a 335/35-18 tire if you use a DSE minitub. There are no modifications required on the AirBar. This is the setup we are using on Velocity.
For the exhaust...the rear axle is moved so far up into the car that it is a straight shot from the mufflers under the rearend into some custom tailpipes. Again, this is how we did the Velocity Camaro. For those using a 2.5" diameter exhaust I beleive the Frank at Prodigy has a special tailpipe available the goes over the axle for those cars.
With either tailpipe setup mitering the front corners of the fuel tank makes things much easier. If you are considering a stainless tank from Ricks Hotrod Shop, he has this modification as an option on their tanks. I think DSE may do their tanks this way as well.
Of course, with any gas tank setup you will need a billet gascap from Preceision Coachworks!