I am a crop insurance claims supervisor, but have worked around property people for 25 years now. Best advise is, contact a local, reputable agent. But I will give you my two cents worth.
I work for Farm Bureau Insurance. As a rule we have an office in most every county, espcially in farming areas. There are other good companies as well. As a general rule, the standard homeowners policy would cover your tractor just as any other personal property. That is, if you just have one or two, and they are of average value and you just tinker around with them. You would be subject to whatever deductible your policy has.
Most all companies offer specific coverage, this is where you list the tractor individually and put a value on it. If the underwriter agrees with your value you are all set. You may have to supply a photo, or value from some sort of published listing to justify your figures.
Most farm policies offer a "blanket" coverage where you specify how many dollars of coverage you want on feed, hay, machinery, livestock etc. You generally need to provide an inventory and insure at least to 80% of value. Here your antique would be lumped in with all the other machinery and be covered for the policy perils at Actual Cash Value (ACV). Here again, you can specifically list an item for a value.
Farm and or Homowners policies also include liablity insurance to cover you in case you injure somoene or something through negligence. As we all know you can get sued for anything. You can genrally buy increased limits of liability or an "umbrella" if you are worth big bucks and want the increased protection.
Everything I have mentinoned if for the person who is doing things on his own property or showing and going to parades occassionally, and not charging anything. If you start making something a business, then it's a whole different deal. You would need a commercial policy. Same basics, it is just more expensive. Occassionally selling items at flea markets and auctions is not commercial. It is when it constitutes the majority of your income.
Sorry for the long post, Gene