After doing a build in my 2002 Ford Ranger Ext cab I'd say it's possible, but you're really going to be cramming. I barely fit a single 18 in the back of mine. 6.5 cubes with a triple baffle on the front, .75" wood etc. you can fit about 7.2 cubes before displacement, all single baffles etc. if you don't build into the area below the hump in middle and staying below the window line.
So maybe a 2:1 ratio 4th. So honestly it's possible, but lots of angles and lots of fun building an enclosure.