Pedestal Mount Question
 

I would like to mount my radio in my 1996 GMC Sierra pick-up utilizing one
of those 'Pedestal Mount' devices that screw into the transmission hump. How
much clearance is there between the transmission hump and the bell-housing
of the tranny? Is there gonna be anything in the transmission that I might
damage? What length of self-tapping screw should I use?