Two options are open, the first is to get a second hand head, if you do get it pressure tested first, these heads are very durable and this is unusual. As the head is cracked i would suggest that someone else has replaced the gasked and torqued the head down incorrectly, or not done the job properly.

Option two is to buy an engine complete, before parting with cash insist on it being in the vehicle, and run it thoroughly and look for anything abnormal. This option will give you the opportunity to study the engine under load, and when it is fully warmed, and allow you to check for smoke, back pressure, etc.

Another thought is to do what i advise people to do is to spend slightly more money and buy a complete vehicle. Accident damaged, insurance write offs, etc are usually available, use the engine and sell off all the other bits, this will recoup your losses and you would reasonably make a profit as most parts are sought after. Stripping down a vehicle will give you more of an insight on how a vehicle works, as these are bolt together vehicles, they are relatively easy to strip. You can accumulate a number of spares for your vehicle also, spare wheels and tyres are always handy, as is much of the interior trim.