This is easy - has the engine been ruined or has it not been ruined? I'm guessing the seller knows more than they are letting on - and that you're going to need a new engine. If not it's a no-brainer.

If the head is warped or cracked--then your purchase will be instantly way more expensive. But, the price is EXTREMELY tempting!! See if you can find out more info from the owner. Service records? Will it start/run at all? How many times did it overheat?

I'd be interested to know how you make out, and IF you buy it--post some pics... Just use common sense and caution...

-GH