it goes without saying that before you start working on a fuel related problem.
you must insure the electric system is all in a-1 shape.
I had a problem once, run a while then stop, then cool down and run again.
it was the coil ??????? just changed the coil and things cleared up.
is the distributor shaft still in good shape, the top bearing can be worn and that will let your points move .020 - .030 I got a new distributor, but if you can find the right guy he can replace that top bearing if its worn.
at this point anything and every thing is suspect.
these tractors are old and so many things can cause you problems.
when you get it right it will idle at 400 rpm's and take the fuel when you sink the plow or disk in the ground and open the throttle.
keep us informed of your progress.