Well, upshot is the bloke was trying to tell me "No, that's fine, its not a water-cooled head, I've done hundreds of bike heads, Z900s, twins, singles etc and heaps of them have looked like that and I've had no trouble with them at all. It'll be totally fine."
"You can't be serious, everyone I've showed it to said that head is toast. Can you guarantee me 100% that when I put this back together it's not going to implode on me at 110Km/h down the highway?"
"Yep, it won't be a problem. But if you're not happy I'll reco another head for you."
"And charge me how much?"
"Nah, I'll just redo another one if you're not happy, but it'll be totally fine like it is."
"Alright, look, I'll take it and get a second opinion, and if they say it's toast, then I'll get you to redo a good one."
So, off I trundle to my local bike workshop: "Would you put this engine back together?"... "Nope".
Off to the other machinist in town... "Would you put this engine back together?"... "I wouldn't touch it with a ten foot pole. A lot of guys will tell you they can chase the crack and re-weld and whatnot, but it'll never be the same. Just get a new head and be sure."
So, I rang him back and said, sorry mate, you're the only bloke telling me it'll be fine. I'll bring another head in and you can redo it for me.
So that's where we are... I really don't trust this guy now, but he did do my last engine and that was fine, and he does pretty much do all the motorbike work in town and came recommended, so I really have to give him a chance to fix his stuff up (even if he doesn't think it is). Otherwise it's just going to be a PITA trying to get the money back off him...
So, replacement head time!