Well, replacing the torgue tube rearend with an open driveshaft design means you will be also considering what to do about your current closed driveshaft transmission. My advise, job #1: Define exactly how you plan to drive and use the truck. Are you hauling, towing, expressway driving or what? DO you want a manual shift or an automatic, on the column or on the floor. All of this is for determining what the best transmission, if Overdrive is required and what ratio the rearend should be to meet your goal.
Good luck
