Nicely done- I like the way you've recycled some of the gas company's stuff too. <G>
one minor nitpick- I think you will be unhappy with the effects of the galvanized fittings in your headers. (yeah, yeah, I can see that you have brass dialectric sections between the copper and the iron, etc, etc. . . ) my experience is that steel and copper get along fine, unless there's zinc anwhere in the system. . . then things seem to corrode, and often where you don't expect them to. as an example:
We build my dad's place with all copper pipe except for the laundry shutoff valves, which were galvanized with brass dialectric isolation. it took me a lot of head scratching to figure out why 2 washing machines rusted to nothing in 5 years each (I'm talking 'push your hand through the case' rusty), while the drier right next to them had no rust at all. we finally changed out the galv. shutoffs (which were fine) for brass ones and eliminated the 'stainless'-braid feed lines (which were corroding(!)); the current washer is 15 years old and going strong. Maybe it's just the wierd water we have here? In any event, I recommend changing the zinc-plated fittings for black iron at your earliest convienience.
Just a thought. I'd hate to see that nifty little boiler die a premature death.
-Dan