If you're running a Rochester "carburetor" there's a bunch of reasons it could be running rich- - - -mostly because they were never intended to last anywhere near the 70-something years they have been around. When GM started making their own Chevy carburetors in the early 1950s instead of buying Carter, They used the "baby chicken" business model- - - -"CHEEP- - - -CHEEP- - - -CHEEP! The top housing of a Rochester B with only four screws holding it on has a bad habit of warping- - - -creating a vacuum leak that causes the power valve to go full rich and stay that way. There's a way of straightening the housing by heating it in an oven that's a temporary fix. The right fix is to install a Carter or Zenith carb!

You might want to open up the plug gap a little- - - -maybe .040 instead of the original .035 to take advantage of the higher available voltage.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!