The type f fluid was designed for ford friction material which is close to early 727.I have not seen that type of friction material in 5+ years.The friction material in your overdrive housing will be new style paper linings,not the metal impregnated frictions in the forward or direct locations.If he installed a shift kit you won't get that much friction from it shifting anyway.I don't install type f in anything unless you own a old Ford.If he voids warranty because of that type of fluid i would find a different transmission builder.If you have a good external cooler any mopar fluid will be good for your transmission.My experience is to look at the transmission dipstick and fill with that fluid.