American Airmotive NA-75 explained

The American Airmotive NA-75 was an agricultural aircraft marketed in the United States in the 1960s, created by remanufacturing military surplus Boeing Stearman trainers. The aircraft were fitted with completely new, high-lift wings, and one of the cockpits was replaced by a chemical hopper. As of 1980, over 200 Stearmans had been modified in this way, either by American Airmotive directly, or via conversion kits that the company sold.

References

. John W. R. Taylor . Jane's All The World's Aircraft 1965-66 . 1965 . Sampson Low, Marston & Company . London .