Well it depends on how you are going to wheel your truck. If you are going to run it on trails that are moderately to extremely difficult as well as mud then by all means go with the D60 first DEFINITELY. If its just gonna be a street truck and be used on some easy trails the ten bolts will hold up fine. I just got into wheeling about two years ago and being completely incompetent in the ways of building a rig I bought a K5 and immediately put 40" tires. I do moderate wheeling on trails and mud and the ten bolts so far have held up good. In my situation I like to do more difficult trails and learned that 40" tires on ten bolt axles just doesn't work. Yeah they look incredible on a truck but the stock axles just aren't enough for the hard stuff. You also have to include how much you wanna put into additional items to run a D60 or 38" tires there are many things you have to include when making those upgrades things such as possible gear swaps, spring plate swaps, u joints ect for the 60 and a body lift, transmission likage extend, radiator lift mounts, fender trimming ect for 38" tires. If I had to do it over again I would have gone ahead and bought the D60 and then went for the bigger tires. So just figure out what you wanna use your truck for and how much you have to spend and go from there.