odometer speedometer dont match
 

Have a 92 GMC project. I have put switches in the DRAC and calibrated my speedo to correct speed. First time out, checked gas milage and found out speedo is correct but odometer is off by a factor of 1.43.( Odo says I drove 83 miles, I really drove 119 mi.) As far as I can tell in looking at the circuit, the same VSS signal drives the speedo and odo. Anyone seen this before? I bought this truck used for my project so I dont know history and guy I got it from bought at a police auction. (should have known RIGHT THERE!!) Previous owners have been under dash monkeying around and I feel they have had instrument cluster out. Is is possible they might have pulled the arm off the speedo and put it in wrong so even though my speedo is correct, the speedo arm is not in the correct position? I do have a lazy speedo arm, when stopped arm is below 0. That may be telling. If speedo arm is not in correct position, is there a way to get it there rather than trial and error?