Antique trucks that fall into the commercial vehicle class by definition (over 26001 cross combination weight) are a gray area in most states. I think that your first step should be to go to your department of motor vehicles or whoever does licensing in your state and find out if there is a provision for antique registration in your state. I would suggest asking different people the same question. You will probably will get different answers. Getting the thing registered as an antique can be a big hurdle in some states. If you can get antique registration like John has on his GMC, you can probably get reasonable insurance. Being a member of an organization like the ATHS is helpful in obtaining antique insurance.