So I thought I would close the loop on this thread or at least give an update. The weather finally broke I got the Sprinter out of winter storage and bought it some new Michelin Agelis tires, and I bought them from a shop that does the road force balancing. I am happy to report that my 65 mph vibration is gone, even up to 85 mph.
I also witnessed some interesting things during the balancing process. When I bought my Sprinter (Winnie Class B) it came with Alcoa aluminum wheels, and like with most alum. wheels the inside duals were steel. Now here is the interesting part, when the tire guy put the Alcoas on the balance machine they were really out of balance compared to the steel wheels. The alcoas required 2.25 - 2.75 ounces on the inside and 1.5 - 2.0 ounces on the outside. Now not having any experience with balancing tires this didn't mean anything to me until the steel wheels went on, each steel wheel only required .25 ounces on the inside and none on the outside.
All of you out there that are savvy to this kind of thing, is this normal, are steel wheels better than the aluminum ones, or just a coincidence?
By the way, thank you all a ton for the info on the tires and road force balancing thing! Not to mention the info on suspension!
2018 (2016 M-B 3500 Chassis 3.0L V6) Winnebago ERA 70A