need advice on a sq 12 sub

I used to do that too lol.  I'm going mostly low key with this one, plus I want it look as close to stock as possible.  For example, I'm the process of doing a v8 swap on the truck, but I'm staying away from loud mufflers, taking out the lopey cam and gear drive, etc. and running the exhaust in a stock type location and no chrome tips lol.  I just don't want to draw too much attention.  It's not a daily driver, but I don't want to be affraid to drive it anywhere. 

Yeah, it would go over the wheel well and start just behind the back seat.  True, I was playing with the calculators here on the site and noticed that the narrower the port, the shorter it had to be.  I think the best thing to do at this point is to go actually measure the space I have and go from there.  I also have to find somewhere to put the amp as well.  I'd like to sink it off into the tailgate, but I'd then be worried about water leakage.  There's almost no space to put anything in this truck lol unless I put it and the box in the cargo area. 

too small of a ported enclosure will sound worse than a properly sized sealed enclosureCustom Enclosure Design

You're right.  I wont build a ported unless I can either A: get it to the proper size, or B find a sub that will use a smaller venter enclosure.  Otherwise I do a sealed.