Round four-light setups normally use standard 5.75" bulbs like H5001 and H5006 which were common in cars biult before 1975. Remember LEDs don't heat up the light's face and melt snow/ice like standard halogen. If you go with a plastic-faced light with LEDs biult in, you will be scraping snow/ice off plastic but these LED headlights will likely fit without modifications. If you get a glass-faced housing with a LED bulb insert, modifications may be necessary even if the seller says otherwise. Most cars have holes in the sheet-metal buckets behind the lights so overall headlight length doesn't matter but that is not the case in many snowcats. Also, beware some LED headlights have a module on the wire between the headlight and plug that you will need to accomondate.
Sorry, I can't recommend a LED light for you. I bought glass-faced housings with 4000 lumen LED bulb inserts from Octanelighting that were longer than stock headlights. I had to use a hole saw to cut the sheet-metal light bucket's back out and epoxy grease caps over the holes on the inside to get extra room. I know that is not something you want to do.
Some aftermarket LED replacement headlights, especially less expensive ones, are flood type lights. They light everying in front of you with no cuttoffs nor hot spots which is normally great for snowcat use. When its snowing and you turn the high beams on, the high beams' upward tilt generates a lot of glare especially with flood types. My LED replacement headlights use the same flood-type headlight for both the low and high headlamps. I added an extra swith and wired my lights so all four headlight low beams can be on together - to minimize glare when more light is needed.
