Nothing wrong with the use of non aviation specific parts if approved by the authority, once flew a brand new fixed wing whose production fuel cap came from a Ford Falcon as did the coil spring used on the nose wheel. The Dextron oil was developed for GM and its automatic transmissions, we had problems using it in the 76 as after some hours had been accrued in hot weather we suffered a loss of oil pressure yet the oil still passed all the specification tests, presumption by the scientific folk was that in being forced through the transmission oil jets the long chain molecules were being chopped into shorter chains, I'd have thought that would make for a loss of viscosity but apparently not. We swapped to Mobil Jet, no further problems.