kits available for disc brakes

Thanks people. As I've come to understand, there is really no way to upgrade my car to disc brakes AND retain the 4 inch bolt pattern. Just goes to show that an impatient novice will make very costly mistakes! I have just purchased new Cragar SS wheels and tires that would be useless if I upgrade. What a dumb mistake. Now I am at a real crossroad. The car is a slant six. I really wanted a V8 and thought that I could easily upgrade to the V8 since the body and paint were so nice. If I did it right, I would need a new engine, tranny, driveshaft, rear end, wheels, radiator, and front disc brakes. While the car is nice, I'm thinking it would be much cheaper to sell it and start with a V8 car. Any opinions?