Just out of curiosity how do you blow the motor up so quick regardless of overheating? If you see it over heating don't keep driving it..... A motor can take quite a bit of heat before it gives up the ghost. I don't know the whole story behind the engine but I will say this improper installation could also have played a role in the demise of your new engine. A few problems such as air in the coolant system will cause excessive heat, bad thermostat, or even the use of a fan with insufficient CFM's.
It is customary to do a compression test prior to installing any imported motor regardless of whether or not the "seller" says its "good." You have to expect the worst when you import a used motor because if the previous owner was a enthusiast then you know it's possible that it may have had a hard life.
And FYI am in no shape or form affiliated with said importer just throwing in my 2 cents nor am I trying to bash you. Shit happens life goes on