* Engine size: This is crucial as different engines were paired with different transmissions. Common options for the 1986 K10 were the 5.7L (350) and 6.2L (383) V8s.
* VIN number: This will give me the most accurate information about the transmission installed in your specific truck.
Once I have this information, I can look it up in the appropriate service manuals and provide you with the correct transmission model.