312P was a 3-liter v12 that was also used in Formula 1 cars. 330P4 was 4-liter and may have external differences from the 3-liter. It would take a lot of work to install a detailed engine in the Fisher 312P kit as the casting is quite thick and there is no chassis detail to speak of. I have one of these, it's a beautiful replica of a beautiful car, but to me it's destined to be a curbside model.