though 400hp is more easily obtained by a stroke 351 than a regular 351. I've seen 400hp 351's many times before. I would just use GT40p with a good port job and 1.94/1.60 valves. use roller cam with 230/236 dur. a good intake with headers and 650cfm carb. 351 is a good way to go if you just want 400hp, if you need more then stroking is your best friend.