Harnesses that provide a clean tach feed for factory ECUs allow older cars to keep their original dash functionality

https://www.scribd.com/document/1014450831/From-Principle-to-Automobile-How-Modern-Electrical-Wiring-Harnesses-Power-Automotive-Development-190884

Harnesses that provide a clean tach feed for factory ECUs allow older cars to keep their original dash functionality after an LS swap.