If you keep the 301, people put new intakes on original car or new cams, possibly headders, you get the picture, the car would still be numbers matiching, to the block at least, as the block is unique to the car, it has the sequential numbers from the car's Vin stamped on the engine pad, the hi performance parts you would put on, like the intake, I'm not shure if it would cause that part to become non numbers matching because, nothing says the original intake is original to the car because, yes it does have casting numbers but, has no refrence to the car itself, meaning numbers like the sequential vin numbers. If you changed the block all togther, the car wouldn't be numbers matching.