MaSnaka John How much room do you have between the aircleaner and the hood with it closed? If you have a 1/2" or more, add a couple of top carb gaskets. 2-3 glued togeather should give you the added clearance to let the choke open fully. Try and retest the clearance again. You should be OK. This way is cheaper than buying a new manifold. Buy an O2 bung from either Summit or Jegs and have it welded on, after testing put a plug in the hole to seal it. Use a little antiseize so you can remove the plug when needed. Stay with the carb at this time also. Lets get your basics fixed first before going crazy.
Rick L.