Tractor Repair: spark plugs, international harvester, gas tractor

Question
I have an international harvester 464 gas tractor and I cannot get it to run right.  I'm trying to replace the plugs and got a set from Napa. The plugs size is 15/16 and  I cannot find that size of plug socket anywhere.  I've tried several different 15/16 deep sockets and none will reach the plugs.  There is very little clearance in the plug well.  Any insight into how I can change these plugs would be greatly appreciated.  The tractor itself seems to have been running way to rich and flooding itself out. After doing some research I replaced the carburetor with a brand new Zenith (the only one I could find for the 464), replaced the wires, cap, rotor, and air filter.  The tractor will start now, but will not run over 600rpm and will stall out after about 30 seconds. I'm at the point where I am willing to try just about anything.  Thank you for any insight you may be able to provide.

Answer
  I have a Craftsman deep socket that I use on IH tractor spark plugs, but I think the size is 7/8, not 15/16.  I have not seen any spark plugs that are 15/16.  Not sure what to tell you about not running over 600 rpm and stalling.  If it's getting enough fuel, air, and spark, it could be that something is not right with the new carburetor.