Will 340 HP manifolds fit 360 crate engine?

My first post in the tech section, so I hope this the right spot for it.

I have a 68' dart that I want to swap out to a v-8 from a slant 6. My problem is the exauxt. I have some 1968 HP 340 manifolds and the engine is a 400hp crate engine. DOes anybody know if I can use those ex manifolds on the magnum engine? I figure I might loose a little hp by not going with headers,but I want it to look as stock as possible under the hood. ANyone try this or are these and natural bolt on for it?