We bore out the Model A Manifold to Model B sizes & hand blend the throat to runner area. This gives nearly the same power gain on our engine dyno as installing a model B carburetor on a stock "A" manifold.
Ultimately installing this manifold & a Model B carburetor is the best combination of factory era manifold & carburetor.
Contact us at the shop to arrange this modification to your "A' manifold, or we can supply you with a new manifold with the modification already done.