I have made a few 4.5" large trackballs Atari like replacements and I thought that many just need to upgrade their existing optic boards or wheels.    I have a kit that replaces the drum wheels and old optic boards.   The kit has two new Happ Red Optic boards, new brackets and two new wheels. 

OPTION FOR STANDARD SPEED WHEELS,  50% FASTER WHEELS OR SET OF BOTH SPEED WHEELS.

How to adjust after installation see this link:

https://youtu.be/sPd7WN5QCOA

NOW COMES WITH PLUG KIT, TWO MOLEX 4 PIN PLUGS AND EIGHT CONNECTORS FOR YOU TO CRIMP TO YOUR WIRING( 20 GAUGE OR SMALLER )

OPTION: PREWIRED Y-PLUG USED ON 3" TRACKBALLS WHICH INCLUDES TWO PREWIRED MOLEX 4 PIN PLUGS, FOR MYSELF, I CUT THE END OFF TO WIRE TO MY SYSTEM BUT IT IS EASIER THAN CRIMPING YOUR OWN MOLEX PLUGS.    IF YOU WANT THIS, I WILL THROW IN AND YOU CAN PAY ME THE EXTRA $20 ON PAYPAL WHEN YOU GET THE UNIT.   HONOR SYSTEM.

Last review:  "I can’t even explain how stoked I am to have my Missile Command working properly again. This kit is extremely simple to install and worth every cent that it cost to make beautiful to play again."