I have a similar problem with my 1957 to - 35 gas.
I do believe we are better off that after a short warmup period the tractors run smooth. Rather have our problem than one that will not run and pull strong while at work.
We must remember these tractor fuel systems are near 56 years old.
All I can tell you is insure you have the electrical system in excellant condition. Run non-ethonal fuel, install a in - line fuel filter.
Tune the tractor so it will idle at 400 rpm, if the motor will not idle at 400 rpm 's you do not have it properly adjusted.
When you have it properly tuned, put the disk on and take it out to some open area (engine warm) . When you put the load on the tractor and open the throttle the engine should take the fuel with no he -cups.