I knew Gary was really intent on using the 400 from a previous discussion on this issue, so I never touched on the "cons" of the project, which I had done previously. Gary makes some good points about cubic inches and reliable power.
Gary,
if you run the CHI heads that pretty much locks you into running the CHI intake manifolds, the head's intake port location is such that they don't really line up with anything else. CHI has done extensive development on the manifolds to get maximum power when used in conjunction with the heads, nothing else will have had this development work done specifically for the CHI heads.
AFD heads have a more generic "standard" port location, the AFD 2V head matches 2V manifolds exactly, the AFD 4V head has the floors of the ports filled in, or stuffed, so that they would match up with the Parker Funnelweb manifold.
If you want to spend the money, either the CHI heads with the CHI manifold or the AFD heads and Parker Funnelweb manifold would make a mean 400 cubic inch engine. CHI / AFD could tell you which of their heads would work best for your intended powerband (both manufacturers offer small port & large port versions).
Either choice I would think will make it necessary to fab "custom" made spacers to adapt the available intakes for the 400 block (I am under the assumption only 4V port size spacers are currently available, I may be wrong, but don't tell anybody
)Other than the engine mounting, header and bell housing issues, the other problem I forsee is the alternator, it will be higher with the new engine and probably will no longer fit in the opening of the bulkhead. Amerisport's bulkhead reduction kit could solve that problem for about $1000.
As always, good luck, George