B.c. Beeson

Hey All, This is my first post. The car I'm talking about is a '82 Turbo Diesel with 120k miles. I believe this is the XD2S engine. Back story: my uncle purchased this car for a female cousin of mine and it ran well with no known issues for 3 years. Another male cousin jumped in it and drove 80 (128kph) on the freeway and according to him the dipstick popped out and drained the engine of oil. I don't even know how long it ran like this but now the engine has a noticeable knock. They took it to a mechanic and had a compression test which was within the original specs. That leaves me to suspect the rod bearing has worn. Now my female cousin moved to a volvo and now my uncle wants to sell the car. I've offered $1100 for it and I think he might take the bait but I also want to know a little bit more about what I'm getting into. I plan to use some oil additives to see if I can help smooth out anything and I will be pulling the oil pan to look for shavings. But, in case it is a worst case scenario, does anyone know where I can get a crankshaft, 4 pistons and 4 bearings? I took a video of the engine while running but it's hard to hear the knock. http://youtu.be/94j8Qjc4avQ