Ya know how the question about whether to use a single or a dual plane intake manifold comes up on here a lot? Well, I was digging around, and found this tech article. I'll stick this in the FAQ in case it comes up again, then we will have a readily available resource. Unless you have a woopty doo powerhouse race car, then the dual is the answer.
http://www.mustangandfords.com/techarticles/5244/

 

especially so on small engines.. like 289/302s.. Larger engines like 460's and 455's can use either intake with the right cam and heads. Its dependent on vacuum, and small engines dont make as much as a large engine..

I would agree on th dual plane fo sho on anything smaller than 400ci that isnt a race engine.

nice find Glen!