First time swap started

[ls1nova71]

I'm not sure why the speedo wouldn't work if the needle was returning to zero when powered up, unless you aren't getting a speed signal to it for some reason. However, I would be more concerned with how accurate it is going to be. The sweep of the two are different enough it may cause it to be inaccurate. If you take the S10 speedometer and draw an imaginary line from zero through the center of where the needle mounts, you will see that the other side will land at roughly the 83ish MPH mark, where as if you do the same thing on your original speedo you are going to be somewhere around the 65MPH mark. That's a pretty big difference.