Frank Nixon and Bob Nixon founded Volitan in the 1950's. Frank had gained engineering experience at Lockheed in special programs before deciding to branch out on his own. By 1960 he joined up with Paragon Corporation to form Volpar Inc. based in Van Nuys, California. The new company became well known for modifying Beech 18's from tail wheel to nose wheel, extending the fuselage to accommodate additional passenger capacity to meet airline's growing demand for aircraft. The conversions later evolved into the "Turboliner" with piston engines replaced with high powered turbine engines. With it's success designing modifications, Volpar in the early 1970's developed a bold proposal to modify T-28's from single engine to twin turbo engine as a COIN aircraft for a government contract. The Volpar A-28F never made it beyond a conceptual design. Little was known about it since it was never built, only an artist model was made along with several illustrations on the ease of modifying the plane that was promised to keep costs low. In 1979 Volpar was sold to a Nevada Corporation, the McDivitt Holding Co. In 1990 Gaylord Holdings of Switzerland took the company over after it had filed bankruptcy in 1987.
A few years ago Capt (Ret) Raymond V. Anderson donated to me a rare original hand typed copy of Volpar's proposal along with an introductory letter. The proposal describes best the history of this concept better than I could. Click on the letter below for a link to a pdf copy to read this fascinating proposal.