Wiring and battery tray questions?

[MyR/T]

Hey everyone. I have two questions. First, what goes in the square hole to attach the battery tray to the core support and where can I find one. Second, I have a new 6 pack engine harness with ecu hookup. There are three wires that come off the harness by the alternator as pictured. Pretty sure the two green wires are for the horns but where does the brown wire go. Thanks I appreciate any help.

 

[Chryco Psycho]

Green is horns , brown is wiper washer tank motor
There was a square nut welded into the core support similar to the one beside it in the picture

 

[MyR/T]

Green is horns , brown is wiper washer tank motor
There was a square nut welded into the core support similar to the one beside it in the picture

Awesome thanks