Depens if it's a 263 or a 320 straight 8. Only the 320's had the 4bbl. manifold. You could try this site for help: http://www.buickclub.org/ Good luck!
There is one on ebay right now: http://cgi.ebay.com/ebaymotors/1952...r_Truck_Parts_Accessories?hash=item3efba95461
That's a rare bird and generally tend to get pricey. I had a '52 Buick Roadmaster with the same - the exhaust manifold is made of pure unobtanium.
would you consider the dual intake with the 2 carbs one missing though other needs a rebuild and i can also get the dual exhaust