i have a MAME cab
What device are you using to light up though?
As mentioned earflier, he's using an Arduino.
Short of buying an old Rush light or a Daytona USA topper with race leader lights on it, are you seeing anything you can purchase that will light up like those? I am guessing this applies to people who have old racing cabinets and not modded from scratch ones?
This brings up the question of whether this can be done on original PCB systems.
For systems using emulation, the preferred approach is the one Buttersoft is using: emulator ==> outputs ==> MAMEhooker ==> Arduino/controller ==> lights.
Disclaimer: I haven't looked at availability/pricing of original leaderboards or if repros are available, so you might want to check that before diving into the processes described below.

If you want to create a leaderboard for original PCB systems from scratch, you would need to find the outputs from the original PCB.
- For example, see step 1 of
reply 7 above where I link to the "race leader" lamps in the Daytona schematic.
Those outputs will likely work in one of four ways:
1. The output is designed to directly drive the lamp.
- No need for more power or logic handling, just connect the lamp.

.
- According to the schematics, Daytona is like this.
2. The output is designed to directly control the lamp.
- Needs more power but no logic handling.
- Add a driver circuit (MOSFET? Relay?) and connect the lamp.
3. The output is designed to work with an external logic PCB to control the lamp.
- Probably needs more power and logic handling.
- You'll need to safely connect those PCB outputs to an Arduino.
- Write a sketch to translate those PCB outputs into light outputs.
- Use some sort of driver to power those light outputs since the lamps will almost certainly draw more current than the Arduino can provide.
4. The outputs are on a data bus.
- You're on your own, son. [/Blazing Saddles]

Scott