Quoted from Blackjacker:A few that I think are essential for GNR:
* PinSound board with a speaker upgrade (Flipper Fidelity/PinballPro or roll your own)
* LED OCD and EnerGI Maestro boards
* Upgraded magnet board from Great Lakes Modular
And if you're powder coating your side rails, legs and whatnot, replace the plastic rear glass channel, H-channel and lift channel with steel replacements, and have them powder coated to match, along with the U-channel at the bottom of the speaker panel. Easy to overlook doing those, but looks really sharp when done.
And get some custom grips on your gun shooter handle. (Pics of mine below - basement lighting, super-reflective surfaces and my lack of skill with a camera all combining to make some less-than-stellar pics, but you get the idea.)
Rear glass channel, speaker panel U- and H-channels and lift channel replaced w/ steel versions and powder coated:
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