900, that's going to be tough.
As I mentioned before, Jeff Varasano seems to possess a deck oven that goes higher than just about anything else out there.
Here's a shot of one of his pies:http://www.varasanos.com/Photos950/pages/16_IMG_0514.htm
This is, imo, as close to a Neapolitan pie as I've seen a deck oven ever get.
His oven appears to be custom built by an oven maker in Sweden. Here's the details:http://www.atlantacuisine.com/2009/10/qa-with-jeff-varasano-of-varasano%E2%80%99s-pizzeria/
I traveled quite a bit testing different ovens and I had a very clear list of capabilities that I wanted. I found an oven maker in Sweden named Christer Andersson. As soon as we exchanged our first email, I knew that he understood some of the unique challenges that make pizza baking so different than bread making. Itís precisely because many people think itís all about the coal or wood fuel that makes many ovens perform quite poorly.
Some oven builders sell their equipment based on the fuel and disregard the design, as if any chamber is automatically good if you stuff it with wood or coal.
When I baked at home, I used the cleaning cycle which allows the oven to operate at 800F. But Iíd use aluminum foil to alter the distribution of heat within the oven. So while I used the same electric coil, a dozen different foil configurations would produce a dozen different pizzas. Right there I knew that fuel source was not my biggest problem.
After a few disappointing tests out on the West Coast, I headed to a little town called Boras, Sweden. The oven was the clear winner and Christer proved to be as good as Iíd hoped. The best thing was that during our conversations it was clear that we both had in mind nearly the same design for a next generation oven that is wildly different than anything on the market now. Yet independently, we had come to very nearly the same design. That oven is off in the future though.
For this round we took his basic design and made a few modifications. There are extra heating elements, and also we had to make many component and design changes to get the oven certified by Underwriterís Labs. Christer even flew in from Sweden for the final round of inspections.
Here is the website for the oven manufacturer:http://pizzamaster.com/
As far as Varasano's modifications go... since Christer inspected the oven, maybe he can recreate them, or, give Jeff a call.
I think it's important to remember that although this is one seriously hot oven that gets pretty close to Neapolitan temps, you're still talking about producing a Neo-NY style product, not a Neapolitan one.
Edit: found a picture of the oven:http://www.varasanos.com/Photos950/pages/76_IMG_0626.htm
It's difficult to tell from the photo, but it looks like the oven might be set to 870 F. Either 870 F or 370 C. (700 F.) Considering how much he talks about hitting 800 at home, I'm leaning toward 870 F.