Have the truck appraised and then get insurance on that amount and for any damage that may occur and just have them insure it during the months that you use it. Most places will give you storage insurance also if you have a dollar amount that it is worth. Just like if you had a classic car or something along those lines.
This will not cover you if something comes off of the truck and hurts someone in the stands, that is covered normally by the pull organizers or pulling organization that you run with.
Good luck!