1990 Chrysler Le Baron digital dash

The gauges are not reading correctly. I.E. Full gas reading - but tank is half full. Temp gauge reading at little over half - cold engine. Oil reads midway but does not change as engine revs. No amp reading. Tach works, speedo works, air bag light works, etc. I have run the self test on the dash, and it read no problems. I have unplugged sending units (temp, oil) no change. I have tried switching body computer, ( got one from junk yard, same model but with analog gauges)with no effect. I have been told that there is a difference in the body computer and/or engine computer for the digital dashs. However, in checking suppliers (advance auto, O'Riely's, etc.) I find nothing that notes a difference. The Chrysler dealer said it is no longe available and couldn't answer my question. This is an 18 year old car, so I know there are issues with parts. I am trying to find out what if any diffience there is in the computers depending on whether it is digital or analog ( is the copmuter I tried not working because it is different? Could it be the engine computer? Are there differences?) I feel the dash is ok, and that the problem is in data going to it. So I am trying to determine the correct parts to attempt to solve this problem. Thanks

Randy