If you have the Prevost-installed dash panel cluster, the speedo and tach are a "module", and the associated smaller guages on each side of the speedo and tach are made up of several segments that can be replaced individually. You do have to disassemble the main section to access the individual modules, but in almost no case would the entire dash need to be replaced. It was Dixson's modular cluster system. Both the speedo and tach get their information from the J1587 diagnostic data link information from the engine sensors.