If the car is your DD it's gonna be $ and probably difficult to cover it for the mods. You may be stuck with the old thing of if it gets hit buy it back, strip it and junk it.
You can get race car or show car insurance, but your street driving will be severely limited. I daily drove my GT with a blower, built rear, and full exhaust for 5 years. Luckily the car never got hit during that time. I demodded the car and drove it stock for almost a year and a half. It got side swiped parked on the street over night. Insurance cut me a nice check for it. Very lucky that the car was demodded.