400 engine Help Needed

Check out 440 source.com for some cheap heads that will perform well for a street car.
You can raise your compression in a number of ways, one by simply installing a thinner head gasket. Or machine the deck. If you only want 400hp, that's pretty easy to reach with a 400 engine.

Check out Amazon.com for 'Big Block Mopar Engines'. There are a couple books that are very good and contain much of the information you're looking for.

I would suggest reading (or online search) the last 12 months worth of Mopar Muscle or Mopar Action magazine for the intake information. One of those had an article that tested different intake manifolds and which one performed the best. Can't remember specifically where I read that article.