Looking at D150 terrible spark knock

Definitely leaning towards buying it. A good price will help me justify any work I need to do. Just to disclose everything he is asking $3000 for an 84 D150 with nice body and interior. One solid color on American Racing 15" turbine style wheels. Everything works but the radio. I am thinking offer of $2200 to offset my Saturday afternoon. That'll pay for the time and beverages.