I wrote them too!
Here was their reply:
"The tire/wheel combo is 325/60/20. The tires are "Open Country Toyos" and the wheels are 8-lug, "Ultra Sport Metal Revolvers". The truck has a leveling kit on the front end which raises the front end about 2 inches.
Thanks! -Dave"
I've heard people on here saying that 20" wheels are a waste and wouldn't be found on a real truck. If I don't plan to do any serious off roading and this truck is basically a street truck to haul and tow stuff, I see no problems with running 20" wheels. After all, that's what the 1500's run if you want that option. I think they look sweet.
Also, I looked at the Toyo website, and they list no specs for that tire yet. I'm not even sure it's available yet. An equivalent size on the Nitto site says it's basically a 33" tire. I priced the 18" tire and it was north of $220. 00.