A couple of thoughts on LED headlights:
1. Some 1156 LED lamps are designed to radiate light in all directions like the incandescent 1156. For this application you want a lamp that directs light in one direction, which makes the condition of the tractor's silver reflector unimportant.
2. LED lamps need an effective heat sink if they are to be used continuously. Some LED lamps have no visible heat sink, which may be fine for a back-up light or turn signal application where the lamp is only on briefly. Headlights will be used continuously and heat will build up unless there is a heat sink, typically aluminum fins of some sort, to dissipate heat.
Hope this helps you when you are looking at LED options to replace your 1156 lamps.