Montana does not require proof of insurance to license a vehicle owned by an LLC.
When you do insure your vehicle, speak with your insurance agent and make sure he or she understands your vehicle will be licensed in Montana through your LLC but may be domiciled elsewhere.
Your insurance policy must list your LLC as an additional interest.
If your insurer has a problem with that situation, here are insurance companies other clients have used successfully:
Tip: see How to Deal with a Seller.