It all depends on how far you want to go with it. The 400M is a badass motor but it takes a lot of work to turn it into the monster it is capable of becoming. There isn't a lot of aftermarket support for that motor by comparison to the other motors. If you are doing it because that is what you want to do, you can make it fit. If you are doing it because that is the motor you have right now then I'd say to go get another motor. Unless you have a specific affinity for that motor it generally isn't the way to go.