I've used a slightly smaller version of this one.
It has worked great for me, but my truck also has the factory external transmission cooler. If you don't have a cooler I'd go with the larger version, or perhaps a 9000 or 10000 series if you want to be cautious.
I believe that Dexron VI is already a synthetic blend. If you really want to learn about it, check out the website BobIsTheOilGuy, they have some resident engineers that could tell you more than you'd ever want to know about automotive fluids.