Casey, great pizza doesn't discriminate between heat sources. A firebrick hearth, preheated to the same temperature, using gas, electric or wood will produce an identical pizza every time. When Jeff Varasano opened his pizzeria in Atlanta, he wanted a wood fired brick oven, but the building code wouldn't allow it, so he worked with an oven manufacturer in Sweden to engineer an electric oven that would give him wood fired temps. Here's an example of what he can do with his oven:
http://www.varasanos.com/Photos950/pages/08_Img7080.htmAs you can see, like you, he's not striving for a pure Neapolitan bake time. This level of leoparding, though, would most likely not be possible with even a modded gas oven.
Not that you'd want to go with electric with your need for mobility, but I just wanted to point out that any oven, if it can go to the right temperature can make any type of pizza.
As far as the differences between the look and texture of Neapolitan and coal, the most obvious difference is leoparding. The faster a pizza bakes, the less evenness there is to the browning. With really fast, less than 2 minute bakes, instead of a nice even tan color, the pizza browns/burns in spots. The sugar and acids in the dough play a role, but, generally speaking, the faster the bake time, the greater the contrast between the dark spots and the rest of the rim. As you get into 3-4 minute coal bake times, you can still get some uneven browning, but the contrast is far less.
Texturally, because of the faster bake and rapidly expanding steam, Neapolitan pizza is usually puffier than coal, which, in turn is puffier than NY. The one advantage that longer bake times do provide is crispness. Neapolitan pizzas may be crisp coming out of the oven, but, by the time they're consumed, the water in the core of the rim has migrate outward and softened the exterior.
With all the talk about Delfina and their modded oven, I have to admit, that's a pretty disappointing looking pizza. I don't know why they would go through such trouble to mod their oven and then go with a chain style thickness factor. Your pizzas have a far better sense of proportion.
Delfina's thickness factor failings aside, Scott R has provided some excellent insight regarding upgrading the thermostat. It sounds like you're leaning towards the MB as of late, but I still think Baker's Pride should be a contender, as it, too, can be fitted with a brick ceiling, and, unlike the MB, appears to have a 140K BTU option. Between the upgraded thermostat and the more powerful burner, I get the feeling you're going to be going through an obscene amount of fuel (which, in turn, will necessitate larger, heavier containers), but if you want something along the lines of what you're presently making, I don't think you have a choice.
As Scott pointed out, though, an unmodded 650 deg. oven can make great pizza. Personally, I prefer a 4 minute pizza to a 2.5 minute one. If you look at pizza sales around the nation, 4-7 minute pizzas outsell 2.5 minute pizzas by a factor of what could easily be 1000 to 1. Baking good 4-7 minute pizzas is like printing money. 2.5 minute folks can get pretty fanatical, though, so expect some backlash from your current clientele should you decide to extend your bake.
