how can i get 400hp out of a 318?
potentially cheap build here:
http://www.hotrod.com/howto/113_0304_318_small_block_build/
will end up being costly if you farm all your work out.
another option like mentioned is higher compression pistons and 360 heads.
I do also believe there was a 400 hp 318 with magnum heads but i don't have that build bookmarked.