A little back fill for color: I am working on 2 camaros ls swap projects. Both are my own. 1986 IROC and 1991 RS. I am almost done with 1986 swap, I pulled the OEM harness, reinstalled a C100 harness off ebay. Managed to require power distribution and ignition and can successfully get the starter to work with the ignition switch. Used A4 and B4 on the C100 block.
However, tried the same with the 1991 and it does not work? when I turn the ign nothing happens. I notice B4 on the C100 diagram shows "starter interlock".

Can anyone tell me if there is an additional ignition wire I need to run or if some sort of safety switch is engaged or if simply need to press the brake to start the car? LOL

 

Most likely VATS or shifter related

The 91 will have a starter enable relay behind the DR kick panel, often behind the black tar. Unplug it, bend some scrap wire into a U and bridge the two large wires

If doing an auto to manual then the NSS will be moved from the shifter to the pedal. This safety switch also breaks the starter solenoid power. Manual to auto is the opposite

Consult auistinthirdgen or charm.li for diagrams to fully trace the issue

 

One of the easiest places to check for power when the key is turned is the starter enable relay under the drivers side kick panel.

 

This is very helpful. Thank you!

 

Very good advice, helpful direction. Thank you!