I am 6'-4" with a 35" inseam. I have an older pair of Simms Freestone waders in XL Kings because of my foot being only a size 12. These are plenty large enough for me. I do not believe that Simms offers that model in the variety of sizes that they used to.
I have seen other manufacturers that have similar size ranges, but not many. They are out there, but it takes a little looking. For some reason, I believe that Dan Bailey has a similar size variety for one of their models.
For a vest, the standard size worked fine. It wasn't so long to get in the water when wading deep. I don't worry about vests anymore because a few years ago I switched to a pack and left the vest in the bottom of my bag.