Here my setup that I got complete awhile back.
It is stock carter bbd and part number is 0-2543...
I would thing that a 318 bbd 2 barrell would work but not sure....
Here is a good read: http://www.slantsix.org/articles/supersix/article.htm
Many people use a standard 318 Carter BBD. If you want better mileage, there was a Holley "Economaster" sold after-market in the 1980's. You can find new ones for sale sometimes on ebay. It had better atomizers, flowed a bit less air, and ran a bit leaner, which might be a better match for a slant anyway.