I finally got a chance to do some measuring. The existing subwoofer box has .37 cu. ft. of sealed air space. So the existing box is not large enough to accommodate a 10" sub even though one would physically fit. I can make a box fit into the factory spot that will have .6 cu. ft. with a top mounting depth of 3.125" to accommodate most shallow mount 10” subs.
I just don’t know if all the work will be worth adding it into the factory system. So if this is gonna happen, I need to start looking into RMS ratings, signal processors, mono amps, capacitors… Oh crap, here we go again!!