Thanks for words of welcome folks!
78_SaltLick: This didn't come off of craigslist, it was actually advertised in the local paper. Surprised the heck out of me. Oh, and congrats on your 550 trade!
SteveD: I'll post some more pics up in the gallery once I take some more.
74cb750: As to the directional control, those are (bad) pics showing the modification I did to get it to work. The plastic "nub" was worn mostly away, so the only way to get the turn signals to go on was to push the switch quite hard. I took it apart, cleaned it up, and found a brass shoulder washer that I was able to make fit over the remaining part of the plastic nub, and also fit properly in the slot of the thumb slider doohicky. I was trying to show what I did, but the pics didn't turn out very good, sorry. But, the switch works now, so that's cool.
General update: I took it for the first "real" (10 mile) ride today. It rides great, but I need to do some carb work. It hesitates and is somewhat stumbly off idle, pulls hard at about quarter-through-full throttle, but will surge a bit under steady throttle. I've only ever worked on single-carb dirt bikes, so figuring this out will be interesting. Any advice on where to start looking for a fix for that problem would be appreciated. I'll dig through the Tech forum for stuff about that tomorrow. The carbs are fairly recently rebuilt, and the previous owner indicated that this particular behavior is not new. It's livable, so it'll probably be a fix that happens when the rains come.
The left blinkers have a long (2-second) delay before they start, then they blink fast. The right blinkers start normally, but blink slowly. I dug up some info in Tech about that and picked up an EP35 electronic flasher to try, but I blew a fuse when I installed it, so I imagine I hooked it up wrong. I'll have to figure that out too (luckily there were spare fuses under the seat). I'm going to focus on the little rideability items like that for now, and I'll try to get as many miles on it as I can before the rains start for real. I'll probably leave the tank, seat, and carbs alone 'til winter's well underway, then work on those and any other more major items over the winter.
Thanks again for the great welcome, sohc4.us is a wonderful resource full of good folks!
Sean