sub in a 99 ranger

Probably, the best in your situation, is to build a downfiring enclosure.  If you look at the link on my signature, I have a site with my personal truck, a 00 Ranger.

If you look at the last picture, with the subs, look towards the bottom of the enclosure, this is a board I built to level the floor so the enclosure could sit solid. I actually have my amplifiers under there, and have built the floor under the amplifiers also.

As I was working on my truck, that "false floor" was one of the first things I built. I was able to still get full use out of the jumper seats (whatever full use is anyway). The only room you sacrifice is a little leg room. If I wouldn't have built the truck floor up level, I had enough room under there to build that into a small enclosure. Small meaning considerably shallow, but possible to get 2 10" subs.

Don't know if this is about what you are looking for. Just an idea, as I thought of doing it myself, until what I have got thrown in there. Hope this helps.