Rust on plug is from water seting in the recess....No problem....All I can say is get it if the price is right....Klem air box lid,which is rare,and what appears to be a hillside honda head....They were the only company to make a cast water cooled head for the 350,and that was several years ago....The head alone is probably worth $400 +/-......Not very many around.....Radiator set up looks well done as well......
The no pump thermal circulation works very well....It's not a problem....Just remember that it only cools the head,and not the cylinder....If you ride a bunch in hot temps,it's still a good idea to add a fan to the front or top of the engine to aid in cooling.....
Hoodlum