Here is a video where Alton Brown makes a home made Tandoori oven with a clay pot that gets up to 835°
video was removed. Too bad. I wanted to take a look at it.
I've made NAAN a couple of times. I use Peter Reinhardt's recipie from his book on whole wheat bread recipies. I'll try to post it later. I made it on my Weber Genesis. The first time I made it, I didn't use a stone. I took a sheet pan and placed it directly on top of the flavorizer bars after removing the grates. That got me the amount of direct heat I was looking for.
As far as the home made Tandoori, Alton brown used a 4" diamond blade on an angle grinder and cut the bottom off of a large terra cotta garden pot. Then he put it upside down on the terra cotta pan it would normally sit on. So the smaller bottom was now facing up like a volcano. Then he Loaded the bottom with coal and there's the Tandoor oven.