1991 honda accord speeometer not working and s light flashing

Are you saying the air bag light is flashing? If so, some components have a lifetime guarantee with Honda, specifically seat belt related. Regarding the speedometer not working, check fuse 11 -- for the function of the speedometer first. Then there is a diagnostic troubleshooting flowchart that should be followed in the instruction manual -- too much to try and transcribe here. Testing will lead to the cause of the failure.

Suspect crank angle sensor ➕ vss - or circuit problems. The cas is inside the distributor - not serviceable. The vss you stated has been replaced - was the square shaft that drives the sensor replaced as well? Wiring and connector is good shape?