A little more insight about some of the potential problems with the KB blocks, Buddy Bar foundry(use to be Alcoa aluminum foundry in the heyday of Aerospace) use to cast KB blocks, they may be out of business now due to the CA enviormental laws.
I called and talk to Ken Black several years ago about the issues raised on this site and he told me that he had lost his vendor on the block castings and the cores casting for the blocks, he was having quality control issues on the castings cores ruining the blocks castings enough to make them unusable.
Hopefully both of those issues are resolved now