83 Buick carburator issue

Had installed 2 years ago, brand new carburator. Same as original. Mechanic adjusted winter and spring for 2 years. No longer available. Car has a difficult start and then runs extremely rough with first start of the day. However, after about 1 block the engine smooths out and there is no more problem the rest of the day. It does have a smell of fuel when parked in the garage after driving. Occasionally I will run Barryman's b12 through the tank. I also try to buy the 92 grade fuel at Shell or Mobil. Apparently, this does not help enough or at all. Any further help is much appreciated. Thanks for all of your help in the past and now. Cubby