Mini tubbing is an expensive decision. You can use a stock tank with a G Bar but the tank needs notched for exhaust pipes. (The old version atleast) To do it right you need 11-12 inch rims which makes them much more expensive. As the old saying goes...snowball. Well worth it though.
Mini tubbing is a slippery slope of expense. The kit is only the beggining, then narrow the rear (do not have to but most want a deep lip wheel), 12" wheels, 335 tires, Cha Ching!