Many of us have that one thing we are crazy about and collect. It can be hard to make our family and friends understand why we are so crazy about it. My brother-in-law collects vintage t-shirts and sneakers, my husband collects toys and comic books, and my dad collects coins. For Leroy Johnson of Angus, cars are his thing. He has more than a dozen on his farm, and his recent purchase has the community all a buzz.

For collectors, there are few Mustangs as highly prized as the Boss 429, as only 499 were built. The car was originally designed to compete in NASCAR against Ford's competitors...