An ADC 9" should be fine as long as the driveshaft angles and mounting are solid.
Here's an example of a similar setup. I hesitate to recommend it from the POV of cost in terms of engine assist for automatics because it's only reducing engine operating efficiency in that context. The only payback is if the vehicle's owner has a manual transmission and can operate on battery power alone instead of using their engine at low load AFAIK.