what size BB stroker is best for race only with stock block?

Is that question is for me Bob?

Then I'd say start measuring and search the books! I don't have a quick answer as to what rods are out there to say will fit in what, but I'll have no issue with a use of another companies rod. A custom rod and/or piston may very be needed.

IIRC, slant 6 guys have used a Mitsubishi rod in there engines.