[Oldsguy]

Denis, as far as I can remember most all Holley carbs are squarbore which means that both the secondary (two back holes) and primary (two front holes) are the same diameter. There may be some monster sized carbs that Holley makes that aren't but generally speaking.... Therefore, you need to buy a manifold that not only fits your engine but fits the carburetor and has a corresponding squarbore pattern. You should be able to find a nice performer manifold from Edelbrock that would work fine or perhaps an older model like an O4B like Joe mentioned. I would recommend that you avoid the Holley Dominator, the Edelbrock Torker, or the like. Those manifolds are single plane design and will not be as street freindly, they are intended for a higher rpm range and may not allow your engine to develop a good vacuum signal off idle for all the amenitys needed like power brakes. You can find carbs on Ebay just watch out for cracks, corroded areas around the front and rear water ports, and galled holes on the carb mounting surface that might have stripped threads. Usually sellers will address these items but sometimes with a caveat that it is "easily repaired". A condition like that may not be. Anyway, good luck in your search.
Dan