what do i need?
I think the XE268 is plenty of cam for that motor. Or even a Magnum 268H.
Why so hung up on the 400hp number ? You should be more worried about what ET and how streetable you want it and less worried about ahp number.
I just dont want to see you stuck with a race motor for a street car. Trust me thats what I got myself in to. I can say I have a 500hp 340 but hopw street use will I get out of it ?