97 olds 88 engine dies at steady speed 50-55

I have an 97 olds 88 that the engine dies when holding a steady speed of 50-55 on the road. The car will be running smoothly without misses, etc. It never does it when accelerating or decelerating or at a lesser speed. Also the instument panel is black, none of the lights are on. The has always restarted, but sometimes runs rough and will have to restart. Any suggestions?

Welcome to AF, I'd start with checking the fuel pressure first, then, when it stalls, try to see if you have sprk and/or injector pulse, many things can cause this and the diagnosis will be diffiuclt.