One of the"problems" with a 6.0 is that it "shears" oil. Its starts out 40 weight & in about 3000 its 30 weight. If you change oil on a fairly quick time frame (most guys here go 5k), its not that big a problem. However, you just spent +/-$500 and are going to use oil thats twice as expensive. If you don't need the lower viscosty because of surging or cold weather starting, you are seriously wasting a pile of money.
There is no doubt that a by-pass filter is a good thing, but synthetic oil is wasting money unless its needed. If you are going to go synthetic, go find some Schaeffer's 9000 5W40. Its one of two that are VERY shear resistant in the 6.0, and if you take OA's on a regular basis, (5k, 7.5k, 10k, 15k, 20k) to determine when to change, you'll recoup the cost of the by-pass and more expensive oil. I'd be surprised if you can't get 20k out of the Schaeffer's. The AMSOIL will shear just like dino & be 20 weight in a few k miles.
I've used regular Delo 400 15W40 year around, and change at 7.5k intervals. It shears to 30w, but the truck runs fine - no surging, no smoke, fires right up & runs smooth. My OA's have shown the oil working well at 7.5k. It costs a bunch less than synthetic too.