What kind of parts are you looking for? The 400 is a 351 cleveland with a longer stroke and a much taller deck height. Edelbrock is supposed to be releasing a Performer aluminum head for the 351 cleveland which will work on your 400. I think there's some intake manifolds out there for the 400 (or at least a set of spacers to run a 351C manifold). I'm not sure about headers. Internals probably won't be needed unless you're getting crazy.