I have had experience with those carbs, using two on my 261 engine. a single carb will give better mileage and better wide open performance.But at part throttle, running on the small primary of the staged 2 bbl, will reduce throttle response and power.I know a few guys who ran one with those results. An older Rochester 2bbl like the 2CG? works well.Andre's suggestion of a Holley 350 will also work nicely. I tested a number of small 4 bbl carbs on my 261 engine using a Clifford heated manifold.I used a shut off on the water heat to test both heated and non heated operation.I gave results in past posts about the carbs.My person opinion is for street use, a dual carb set up is the better than a single 4bbl of the same CFM.The Clifford 4bbl intake, the only one avaiable for my engine has too large a plenumn for low speed street use the way my engine is tuned.The large plenumn fools the engine into thinking the carb is larger. Perhaps a 250 will respond differently.
