Stock is best imo if you want to keep the 35-40mpgs. I'm -1/0 and its ok but you really lose a lot of top end and should expect it to wheelie even more. I get 90 miles to a tank now but that includes an pc3 map. Was 120+ to a tank stock.
Stock 17/39 is good for just highway stuff. Depending on what all of your riding consists of, you could even consider going a tooth larger on the front or a tooth smaller on the rear as well. 18/39 or 17/37 or something similar. Never done it personally, but those sprocket sizes should be available. And you definitely want to be wearing ear plugs while riding. Helps a lot drowing out the bad noises, but you can still hear plenty good.