Most of the bad overdrives I have seen it was bad clutches not hard parts although I have seen one of the big roller bearings in the back go bad and one set of planataries go bad in one. I run type-f in my personal stuff and tow with the OD all the time

Dexron III is close but not quite as slippery as mopar +4.

Either way you choose I don't think it is a huge differance, I just like giving mine the extra little edge and yes, you can feel the differance in going from +4 to type-F while dexron III will be in the middle.