Here is where I would start. Gap the points at 0.020. Turn the engine over till TDC is found. Make a mark on the front pulley. Make another line to service as a pointer.  Turn the distributor till the points just open (either #1 or #4 since we just found TDC and did not check which cylinder). If the intake manifold does not have a 1/8 inch pipe plug  in it drop the carburetor and drill and tap for one. Hook a vacuum gauge here. Start the tractor and see how it runs. See how much vacuum shows on the gauge. If below say 18 inches, move the distributor till you get the highest reading. See where the timing flashes on the front pulley. You may want to mark the front pulley off in say 10 dgree increments to help with that. The old addatage, timing it to highest point of vacuum is what you are trying to do. Do you have acess to a dyno. I would not go pull before I put it on a dyno and check the performance of the tractor. Questions?