1989 GM 5.7 Litre Froze up?

1989 GM 5.7 with 170,000, I was away for awhile and my wife was using my truck, she said it died after a loud noise and then wouldnt re-start. When I returned, battery was dead, no juice at all, put in a better battery, and got just a click, cleaned all connections at battery and starter, same thing, tested starter and solenoid, which was ok, but still just a click, oils is black, no shavings or water on dip stick, tried rotating crank at bolt, will not budge even with plugs out, she cant tell me what kind of sound it was when it died, I thought maybe just a back-fire, now I am worried, is there an easy way to see if the main bearings spun? Or if there is major damage inside to look for, I really need this going, thanx