Here's a fun item I found while on vacation that's been a big help with this.
Myself and a friend went into a small, antique car garage. The kind of place that's piled floor to ceiling with NOS parts dating back over a hundred years. Plus books, memorabilia, magazines, salesman samples, and pretty much anything you can think of.
Well, I found the (quite small) motorcycle section and found an original KZ400 shop manual from 1975! Admittedly I do have a download of the manual, but I prefer paging through a physical book so much more.
A bit beat-up looking, but still has all it's pages! Even has the color wiring diagram, which will really come in handy when I have to go through all the electrical on the bike.
Well, the engine has to come apart further before it can go back together. When we were taking the cylinder head off, we accidently broke the seal on the cylinder base gasket, so that's gotta be replaced.
Happily, the cylinders look to be in quite good shape. The pistons are also nice, with only a thin layer of black carbon on top that easily scraped off.
The main problem will be trying to remove whatever baked on green stuff is all over the gasket surface of the crankcase. I don't know what it is, but it's stubborn.