My question is now, is it worth a repair? The rest of the motor seems aestheically okayish but since I don't know the history of the bike I could be repairing a lemon from the top down. The valves seem alright as well but there is a big deposit one pair of exhaust valves. On the bores there is a bit of surface rust but that doesn't seem too bad. There's no water or fuel in the oil so the rings seem to be holding up.
Since head gaskets are NLA and Grame France is charging the guts of €100 for a gasket, is it worth the risk? The alternative is a new motor and break what I have
A few photos for clarity

