To use the QT bell on a Challenger TR6060, you have to change the input shaft and midplate. It's about $650 for those parts, plus another $916 for the bell. If I went aftermarket T56 Magnum, the bell is still required so not sure it is fair to include that other than to say that a used TR6060 at $1800 would run $3366 in total to get it bolted to the motor. Compared to $1800 if I could use the TR6060 as is, the $3366 is a significant difference.
As far as I know, no one makes an aftermarket bell to work with the Mopar TR6060 that put's the starter on the drivers side. There are aftermarket ones, but they keep the PS starter location.
A used TR6060 and $650 in parts to use the aftermarket bell isn't a bad price, still $1000 less than a new T56 Magnum. But it still requires the output adapter and special drive shaft, plus you don't have a speedometer output so additional parts. That kind of eats up the $1000 savings pretty fast and makes it a little harder to justify. If the TR6060 just fit, then it makes more sense, in my mind.
