There has been a lot of discussion lately on rebuilds and cam selection. Check the archives. I have run a 600 Holley on a Clifford 4bbl intake on a modified 261. Also used a 500 Carter, 500 Edelbrock, 2 Holley Weber 2 bbls, and originally 2 Rochester B's on on an Offy dual carb manifold.These set ups were on the same engine.All the 4bbls needed some tuning before performing well. The Holly acts larger on The Clifford than you might think. The relatively large plenum under the carb allows a lot of mixture to accumulate ,fooling the engine into thinking it has a larger carb.The stock jetting was ok and the truck ran as well as the smaller Carter and Edelbrock. For my engine , all the above single 4 bbl carbs were more than needed.I now have a Carter WCFB 400 cfm 59 Vette carb installed.This may be the best of the bunch.If I were to do it from scratch, 3 small one barrels on a log intake would look cool.And I bet it would carburete well with a little tuning.