Quoted from Pinball_Nate:
In other words, you take the light brackets completely out and replace the whole thing with these boards.
Yes. The green 555 boards replace what Stern produced.
I don't know where you are at on your wiring know-how, so at the risk of insulting you, here you go.
Your GI lights derive power from one red wire and one white wire that are located on connector J-1 at the rectifier board. In Stern blueprint terms, the rectifier board is referred to as A2, also shown here as Transformer. All three A2 connectors, J-1, J-2, and J-3 are shown here.
Screen Shot 2018-11-18 at 10.18.24 AM (resized).png
Your red and white GI wires are shown below in this pic.
Screen Shot 2018-11-18 at 10.17.50 AM (resized).png
In this pic, only connectors J-1 and J-3 are shown. This is the transformer drawing. Compare J-1 in this pic to J-1 in the first pic. They are the same but drawn differently with the transformer drawing having more detail, such as wire color.
The J-1 connector is your play field wire connector. It has 4 wires (go take a look on your pin).
a) wire #1 is your red GI return wire. In blueprint terms (b/p) this wire has the address of A2-J1-1
b) wire #8 is your white GI wire. Address A2-J1-8
c) wire #6 is your blue-white wire that that powers your flippers. You will pick this wire up at the under-play-field 1 amp fuse holder. Address A2-J1-6
d) wire #7 is your blue feature light wire. Address A2-J1-7. This blue wire feeds all of your feature lights. On those green 555 boards I linked you will see a connector labeled as "common". This blue wire is your common wire.
The J3 connector: This is your back-box wire connector.
e) You will see that A2-J1-7 blue (common) splices to pin #6 on J-3, or A2-J3-6. This spliced wire feeds all of your feature lights in the back box.
Screen Shot 2018-11-18 at 10.17.26 AM (resized).png
This last pic is of your lamp driver board (In blue b/p terms, the lamp board is referenced as A5 which is not pictured). This shows you the address of each feature light. This is a crappy hard to read copy, but it tells you that your Game Over light is a grey wire with white stripe. Address is A5-J2-11.
And your Middle Rocket 1K light is a white wire with Address A5-J3-11.
Screen Shot 2018-11-18 at 10.20.24 AM (resized).png
With this information, you should be able to install the green 555 boards with little problem. Just think in terms of feature lights on the A5 lamp board and the common blue wire on A2-J1-1
Good luck on which direction you take. Happy b/p studying.