Now that I'm Googling it for info, it seems it may be only officially 150 watts, since it's similar to the 150; the tech that did the work on it measured its output, and claimed he had it around 210 if memory serves, with more to go but said he was concerned the guitar cabinet he was using would blow if he turned it up any more. I have about zero technical knowledge myself, so I took his word for it. In any case, it's weird and plenty loud, two qualities I like in an amp.
http://www.soundcitysite.com/sc_webpages/photo_page_15.htm#x188_1.1Don't have any wiring shots. It came with GEC KT88s, their date code indicated 1974 according to what I found online. Power tubes didn't seem to make much of a difference to me, I tried it with new JJs and old Peaveys (stock tubes in a Classic 400 I sold, not sure who actually made them) so I sold them. They paid for the amp, matching cabinet, new power tubes, and some misc tech work to get the amp back into fighting shape... with a good bit of cash left over. Eventually sold the cab, it looked good with the head but wasn't such a hot performer. Preamp tubes did make a difference, it sounds best with the ones it came with. The one that still has discernible markings is a Mullard.
Over the years I've owned all sorts of amps, as has anybody that's been messing around with music I imagine. Still own a Mesa D180, a couple little cabinets, and 2 Genz Benz amps that I like but make for boring pictures. I should sell most of it, but I haven't yet been so desperate for money that I'm willing to part with this cool stuff for the tiny amount of cash it would bring in, never mind dealing with the hassle of trying to sell anything. It doesn't take up too much space stacked in the closet.