non dunable overrides including the 1-6 require you to be extremely cautious. If you try to downshift and your not at a complete stop, you can pretty much say goodbye to your transmission. And if you let off the throttle and not pull in the clutch can cause trouble.
Dunable overrides are spring loaded which keeps the transmission from backloading. You can use a dunable like a regular transmission without the need of worrying about pulling the clutch when the throttle is let off. Use it like a normal tranny and have the ability to shift like an override. Except im not 100% sure about downshifting.
Hope that helped answer your questions. :cool: