So.. a quick look at the FAST rule book says this.... M0 (Open Modified) Rules The Open Modified class (M0) is for exotic cars, and cars that exceed any of the above limits, but are otherwise street legal and on street tires. Cars that bump up from M1 also go to M0. For safety, doors, hood and a complete firewall are required for ALL Modified cars. Tube frame and kit cars are allowed in Open Modified provided they have a minimum of two seats, are fully street legal, and meet all safety requirements. and...this... R1 – Race Tire This is our top class. Any streetable car on race tires can compete here regardless of modifications as long as it meets safety requirements. See Safety Rules for requirements related to open-top cars with race tires. So the current class killers are Lotus 7 clones with LS engines....the question is can a full body mustang be competitive?.....for about half the price. The gauntlet has been thrown..project Foxbody.