Not that this is a solution, but if you're looking for a 2 bbl manifold for the 230-292 6, late 292 (late '70's-early '80's) had 2 bbl carbs. They used the rochester 2SE progresive 2 bbl. This is the same carb that was used on the early '80s Chevy ad Buick v6. It's bsically a primary and seconday from a Q-jet. Not a bad carb, though I find it a little finicy to work on.
