My truck is a DD, also I tow a 5k welding rig at least 3-4 times a week with no problems. It pulls pretty strong through first even without power breaking and when it shifts to second the charger lights. It spins until you let off or wreck. The only time spoolup is an issue is if you try to pass in 5th and not let it down shift. It smokes like a freight train and is laggy. A downshift to fourth and it spools fast and doesnt smoke. Dustin loaded a trans tune in my truck to compliment the charger, it downshifts with less throttle input and the shiftpoints were raised to about 2k rpms. The only time I wouldn't recomend this turbo would be if you towed very heavy often. 8-10k+. If you tow heavy occasionally, once a month or so you will be fine, but day after day you would probably get tired of the high rpms you would have to run to keep EGT's and smoke in check.
You would need to modify the housing which is not worth it. It will still have the very restrictive exhaust side. Best thing to do is get a different charger. It will prob cost you around the same