A:Answer You have two choices - either you can get an install kit that comes with either a filler plate to conceal the gap or a 'cubby' to add under your new radio (handy for holding a couple of CD cased, charging cord, whatever). You should be able to get an install kit specific to your vehicle that works with any single DIN radio for around $50.
*OR*
There are a few manufacturers out there that make a 1.5 DIN deck. I think Rockford Fosgate is one, Pioneer may have one as well, but there are fewer options