1. Neutral safety switches are for automatic transmission. Don't need that.
2. You ALWAYS push the clutch in when starting. Foot on brake or park brake on.
3. I don't recommend "removing" any harness wires from harness or fuse box. They can be used for any add on's. The markings on wire and fuse box don't matter. Roll up the wire, tie wrap it and tuck in under.
4. No need for a relay. Why?
5. Whether harness covers this or not, it's simple.
One wire from keyed hot to HEI pos.
One big fused wire from battery to alternator.
Fuse box power is wired per instructions. I can't open any of your pics.TOO SMALL.
If you need help along the way, post instruction sheets.

Speedway harness was MUCH cheaper?????? 17 feet long for trucks. 22 circuits. Free shipping. $180


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn