You can get a plow prep, and it wont void your warranty. Many times with the diesel package you get all the plow prep items with it. HD front springs, all the coolers, dual batts, and hd rear springs. The allison must have the pto option from the factory, so not all allisons trannies will have that feature. You have to talk to a commercial sale person, the floor guys dont have a clue. and the allison is a 2200.00 option not 1200.00. the d max option is about the same as a cummins option tho, and alot less than a HO cummins option.
As far as the low reverse goes, remember that the d max, only has the 3.73 gears available, so if you are used to 4.10 rear gears, then the rpms in reverse will be about the same.
that 38K seems high, I demoed a fully loaded 3500 x cab pick up, will all the goodies except leather for 38K, so a cab and chassis should be less. I also looked at the same truck in dodge packaging,with the HO cummins and 6 sp, and it was the same money.
Its been mentioned that the Gm frame still isnt all that strong, but one has to remember that they use a new forming process, that allows them to use a smaller box frame, that is stronger than c channel frames. Its called hydro forming, and it uses water under high pressure to form the rails. They also have added more cross beams, that stiffens the frame. I went to the power launch tour, and all three brands were side by side, and the gm frame had the least amount of frame flex when going over whoops, yet still had the best traction from the ifs. In fact with all three having limited slip rear diffs, the gm was the only truck to go through the whoops without 4wd. They really do make a great rear locker.
Now the ford and dodge people will poo poo this, but I dont care. That is why they make 3 brands. You can have yours, and I will have mine.