I apologize - when I got my insurance I checked the Texas Automobile Rules and Ratings Manual. Rule 71.A.2. currently provides:
2.A motor vehicle that is a utility type vehicle shall be considered a private passenger auto, if it is owned... by an individual... and not used for the delivery or transportation of goods... or for farming or ranching.
Rule 55: Utility type means vehicles (with a G.V.W. of 10,000 lbs. or less) of the pickup body, sedan delivery, panel truck, van type and multi-use type which includes Jeeps, Blazers, Rancheros, Broncos, and other similar type vehicles.
Rule 55 was later amended to increase G.V.W. to 25,000 lbs or less. This must be where my confusion comes from. I never told them I used it for farming, but they insisted that the only way they could insure me was through a commercial policy as a farm vehicle. I've just called my insurance and they can insure me under Antique Collectible for much cheaper than my commercial policy. Learn something new every day - thanks guys.