I am working on a 1964 Dodge Polara. There was not a tachometer except in the electronics for the FI controller which sits on the console. I wanted a tachometer but didn't want one mounted external so I replaced the clock delete with an in dash tach and then also wanted something to show me which gear I was in and so added that and an oil pressure readout where the other round gauges were. The stock Dodge gauges don't really tell you what kind of oil pressure you have so opted for something that gives more information, also wanted to eliminate the amp gauge which was replaced with the electronics volt gauge in the console but don't need to be monitoring that when you are getting with the program. I didn't like having to look down at the console to see the RPM's and not the road. The car has a 528 Ray Barton hemi so things start happening pretty quickly when you get on it, and I didn't like not having driver friendly indicators to operate the car.
Enjoy and criticize if you like, but it is what works for me...... the led's are the gear indicators and the one below the tach is a shift indicator.