1995 Other Chevrolet Models changed to an automatic Transmis

First thing you'll have to change to a speed sensor which i'm not sure if you can get one or not. It depends what transmission youput in. If you put a 700R4 in you might something similar with a 4L60. That may be your cure. The other problem you runinto is you went from manual to automatic and the PCM will never be right because it will always think it's a stick and not an automatic. You are also missing a complete wireing harness that hooks to a 4L60 so don't change the PCM to an automatic thinking that will help. Knowing what type of an Automatic would help tremendously. Youmight be able to use your old speed sensor so don't throw it away until you check other things out.