Again There are no 2bbls common to the 250 in any GM vehicle made in the USA.
The exception is the later 250s with the integral head came stock with a 2bbl. I did forget one other exception.
There is a 2bbl manifold that was made in the southern hemisphere. I've seen pictures of it, I have not heard of anyone getting one up here. Evidently GM did develope the L6 a bit more for south America. There may even be another head for 250 down there.
Beltfed is right you can either use a 2bbl adapter to the stock manifold or an adapter on a Clifford or Offy manifold. If you have the tools you make an adapter plate to bolt to the stock manifold for a 2bbl. You have to flatten the top of the manifold, hog out the stock hole, and make a gasket.
Larry
