Just for reference to OP, 39" km3 measure more like a true 38. I am running 39" km3 on my JTR and under load, they measure 37.5" and are a fairly light tire.
I just replaced my worn out Toyo 37s with Falken 38s. The Falken 38s only weigh 2-3 pounds more than the Toyo 37s. I was set on getting Toyo/Nittos again but the tire shop convinced me to try the Falkens. I am happy with the Falkens and glad I went that route.
Also, the Falken 38s were $10 cheaper per tire than the Nitto 37s....