After searching I'm pretty sure I know what the answer will be, but consider this just that misery loves sympathy.
Yesterday the wife ran the 1994 Blazer 6.5L diesel down to just a little over three quarts of oil. (Getting her to check the oil when she fills up is ... frustrating.) She calls me up on her cell phone saying the Blazer is making this terrible noise, and then holds her cell phone up to the engine so I can hear it. All this time I'm yelling over the phone to shut the engine off. Oh well... Any way I get out to where she's at, check the oil and it's not even on the dipstick. With out thinking too far ahead I dump two quarts of Rotello in the engine and now it's still nearly three quarts low. Have her turn the key and engine doesn't move but starter is really spinning. I lost the plastic cover someone put on the 4L80E transmission so I get under the truck so I can see the flex plate and torque converter. Transmission is spinning just fine, but nothings moving on the engine. I'm going out later today and see if I can spin the engine over by hand, but I got a pretty solid feeling that's a lost cause. Right now it's looking like a broken crankshaft and I'm assuming the worst that I'll need a new engine, or at least a short block. The heads, injectors and IP on this engine are all less than two years old, and the IP was replaced with a new unit. I've been trying to find a builder 6.5L in Colorado but no luck so far. However, I've found plenty of 6.2L engines that I could use for a rebuild. From searching I'm fairly confident that I can use my 6.5L heads and such with a 6.2L block, but are there any issues that I need to look for when I go to check out any blocks? Things like which 6.2 block years or casting would be better, one piece rear main seal, etc.