Once you get the passenger side tube unbolted from the center section, you can take a metal bar or something and go through the center and knock the drivers side one out. I had to do this when I changed the gears in my front axle. Getting the front diff out isn't too terribly bad of a job on a 350, and should be doable with a 6.5. I don't know how tight things are with your CUMMINS in there, but I know it takes about a day to get mine out

. I have to get the engine loose which requires pulling the front end and radiator support out to do, then lift the engine up while the trans is dropped down to get to the passenger side mounting bolts and the drivers side upper. Sure wish I would have done a body lift now as it is pretty tight in mine.