Okay – Now I understand what you’re after. The big block pump bolts onto the small block but requires a short, (5.625" long) shaft. Moroso makes one - Part #22090. Remember that if you’re working a 400 block small block, you'll need to machine the pump shaft opening to 9/16". The BB pump will probably cost you 2-3 horsepower, negligible really – unless your all out racing.

Remember too that there are two different size pickup tubes, 5/8" or 3/4" and that you need to have the pickup sized correctly for the pan you’re using. Go to Moroso's web site and they have all the options..

http://www.moroso.com/catalog/catego...?CatCode=17006

Have fun,
Glenn