carburator problems...

is it a 2bbl or 4bbl? And if your smelling gas and gas is spewing out when you pop the hood then your probably flooding it, which would indeed mean your right in that its getting to much flow. If its a 2bbl then it then take off your air cleaner, find the throttle linkage and loosin it a bit then test it to make sure it opens wide enough to get fuel in. If its a 4bbl then do the same but you might not need to loosin the primary 2 bbls, you might only need to loosin how wide the other 2 bbls open when they kick in. If it runs fine at cruising speeds but stalls and dies while accelerating then the 2 bbls that open when accelerating might open too wide and bog it down. If im wrong someone please correct me. Hope that helps and possibly fixes the problem.

The rate of fuel delivery will depend on the vacuum the motor has, and the jet size. Assuming it has ran fine before and this is a problem all the sudden, points to floeats, or needle and seats. It is pretty hard the flod a motor at cruising speed. The the floats are just too high or the needle and seats are not cutting fuel flow like they should.

I'd also suspect your carburetor accelerator pump. When you floor it, you loose a lot of vacuum and this pump compensates by giving an extra squirt of fuel until the vacuum catches up and can draw the gas out of the venturis.
Daniel

You might also check the timing... does it ping or stutter when you step on it, too? How does it idle? How new is the timing chain? It may have slipped a cog or two if it is old and worn, ESPECIALLY if it is the original nylon coated silent type sprocket. Did you change anything from the point it was running well and not stumbling to when your current problems started? Have you pulled spark plugs and checked them for wetness, soot, discoloration or signs of overheating? Does it overheat quickly? I'm just trying to brainstorm here...
Daniel