American Muscle sells a fabricated set for $100. When I get back to the house, I'll post the number for them. It is a Chevy dealer in Winston Salem, NC. They have very competative pricing for all chevy restoration parts.
I got a set, but it seems they provide the exact block mounting position as my 283 SB mounts. I have heard you can use the SB frame mounts and buy SB motor mounts and they will work for your BB. I am concerned about the relative strength of these mounts vs. BB mounts, otherwise I suppose they would use the same part.
John Walker