So essentially I'm doing the opposite as you. I started with the 315/70 17's because my Ram needed tires. Handles like a go-cart compared to the Ram. Since I have a manual trans, I will probably regear since 6th is useless below 70. And as long as I am re-gearing I will probably regear for 37S and do the lift at the same time.Once I got the caster dialed in to ~5 degrees, its been very good on the road so far. The shocks are a bit stiffer than the stock ones (running rocksports) and don't soak up the minor bumps quite as well but they do a better job with the bigger stuff. Body lean and fading under braking are almost entirely gone now though which is awesome. Won't get a chance to wheel it with the stock tires so can't comment on that.
I'm going to Patagonia's in a 315/70R17 so they should still have plenty of room for flexing. Since those are D rated and a light tire overall, I'm expecting it to be fairly similar to the KO2s.
Why not 37s for you?