I run the BMR adjustable TA and did not lose any ground clearance, although I'm still mounted to the tailshaft. I don't see why relocating the mount to the tranny tunnel would cause a ground clearance loss, though.
However, I would go with the adjustable TA at all costs. This will help with a stock or modified car, and once you start making more power, you'll want the ability to plant the rear more. Most guys run a -2 pinion angle as I do, and that is good for most applications.