Re: Neutral safety switch
You can search "clutch switch" here, or used advance search with posts by me for pics of the 69 clutch safety switch. This switch is roughly equivalent to the NSS function on an auto equipped car; the fat purple and purple/white wire that are part of the ignition circuit go into the clutch switch, and pushing the clutch in completes the circuit and allows electricity to flow from the ignition switch (when in the start position) to the starter solenoid.
Completely separate from that are the reverse lights. On a 69 model with OE manual transmission, there is a "backdrive" linkage (you can search using that term and should find pics of what that is) from the shifter rod to a bellcrank on the subframe rail, and then another rod up to the tab on the bottom of the column tube. When a 69 model with OE manual trans was shifted into reverse, the backdrive system moved the tab at the base of the column, rotating the metal tube inside the steering column, which in turn triggered a reverse lamp switch mounted on the top side of the column housing inside the car, near where the column mounts to the firewall. Incidentally, putting the shifter in reverse and the rotation of the tub inside the steering column also allows the ignition key to be turned all the way back and removed from the housing; in other words, all the backdrive system functions as a safety device, ensuring the car is placed in reverse to secure it when parked. Auto transmission cars had the same type of system to make sure the car was in park before the key could be removed, and column shift auto cars also used the backdrive to activate the reverse lamps similar to manual cars.
If you have the column out of the car, you will see a window/elongated slot in the column housing near where the firewall bracket goes, and through the window you should see the inner metal tube with an equivalent slot. You will also see two small mounting bosses (either side of the window in the housing) where the OE reverse light switch mounted.
Now, all that said, many, many 69 cars had the backdrive linkage thrown in the trash when headers were installed. And if you're converting from automatic, you may not want to go through the hassle of finding and installing the backdrive. You can easily place the inner column tube in the correct place to allow the key to be removed; some folks use wire to tie the tab at the base to something underhood, to keep the tube from rotating. I used 3M stripcalk inside the column to keep the tube in place and not compromise the collapsability of the column in an impact. Then you can use an aftermarket shifter mounted reverse lamp switch and just extend the pink and lime green wires to that location.
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!