How do you wire neutral safety on an LS/4L60E swap without burning up the range switch?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

Other wiring

• 700-R4/4L60/4L60E: An aftermarket neutral safety switch is wired between the ignition switch and the starter circuits using #12 (or heavier) stranded wire, and when adjusted correctly it shows continuity between its two studs only when the shifter is in Park or Neutral. (Lokar, Inc. (via manuals.plus))
• 4L60E/4L80E: Truck/SUV 4L60E and 4L80E transmissions have a factory reverse-light switch on the shift detent rod on the driver's side, and the same switch incorporates the park/neutral switch; swap harnesses wire their reverse-light wires to this switch. (Painless Performance Products (via Scribd mirror))
• 4L60E/4L80E: With a 4L60E or 4L80E swap, a starter relay must be used (not supplied) unless a factory switch on a GM keyed column is used, because the transmission-mounted switch is not capable of handling the amperage the starter solenoid requires. (Painless Performance Products (via Scribd mirror))
• automatic: The neutral safety switch is a safety device that only allows starting in park or neutral (or with the clutch depressed on manuals): when the trans is put in park/neutral, contact closes between two pins and power flows through the switch to the starter solenoid. (Painless Performance Products (via Scribd mirror))
• LSx/Vortec small block; 1997-up: Current Performance direct-fit custom harnesses will utilize the vehicle's factory neutral safety switch where possible rather than deleting it. (Current Performance Wiring)

Transmission control

• American Autowire's Classic Update instructions wire the neutral-safety switch in the starter circuit: purple wire 6 runs from one neutral-safety terminal to the starter solenoid 'S', purple wire 5 feeds the opposite neutral-safety terminal from the ignition switch, while light-green wire 24 is the backup-lamp output and pink wire 39B supplies ignition power for the backup lamps. (Api)
• American Autowire's update instructions state that with a factory manual transmission the purple #5 and #6 wires are connected together if no neutral-safety switch is used, where #5 is the ignition-switch start feed and #6 is the output to the starter solenoid. (Api)
• Lokar's shifter instructions (INS0239, via manuals.plus) require the neutral-safety switch to have continuity in Park and Neutral only, specify wire #12 or heavier, and say that if the fuse panel has no neutral-safety connections the purple ignition-to-starter wire must be cut and routed through the switch. (Manuals)

Confirm against the instructions for your exact parts before wiring. More: Other wiring in our tuning guide.