Scenario: I have a 1987 Geo Speck with a busted transmission. It happens to be a Borg Warner. Now there are significant differences between pre and post '87 Geo Speck transmissions. So, I have to hope that this guy has exactly the transmission I need out of the tens of thousands of permutations possible (different cars, bolt patterns, gear ratios). Am I, or any sane individual going to call some random guy with the hope of hitting a 10,000:1 shot? No, of course not. Nobody’s time is worth so little.
Please take my advice. Do all the for sale posts you like, but try to be at least somewhat detailed when you actually make the post instead of: don’t know what it fits, not sure of it’s condition, not sure if it’s a manual or auto, and don’t even know how much.