So I got her all apart this weekend... every last part removed from the old frame, and the engine ready to mount to an engine stand and start the rebuild. While I've got it apart, what all should I do to it? Normally, I'd lean towards the other comments that say don't take it apart, just flush it out good and try it. When I pulled the carbs, I noticed leaves and pine needles down inside the heads (resting on the long skinny part of the valves), so I figure I might as well be sure.
I also drained what was left in the gas tank... my "gas cap" was a couple of those brown convenience store napkins stuffed in the filler neck. It's kind of hard to tell from the picture, but it's definitely a rusty brown, about the color of coke after you let it sit overnight in a glass filled with ice. I poured some into a metal lid and lit it up, and it took a few seconds to catch, but it did burn.
I also pulled the head covers, and the cams are NOT the color I was expecting. Good news there is that if I turn it over by hand, I don't feel any unnecessary binding, and there's no obvious noises of like grinding or metal hitting metal. I also hit one of the cam lobes with a brass brush, and it shined like new after about 5 seconds.