How to find the index of an Object in an Array

If these two arrays are always going to be paired one-to-one, I'd just make a small class to contain the objects you want, then make a single array of that class. As an example in C#:

 using UnityEngine;
 using System.Collections;

 //Step 1: Define a class that contains the types you want. 
 //        (put it anywhere, I usually dump it in the script 
 //        I'm using the class in, or in a file of its own 
 //        if it's used in multiple places)
 //Step 2: Add the attribute System.Serializable to that class.
 //Step 3: In a script somewhere, declare an array of your type.

 //The below line tells Unity to show this class' 
 //"Serializable" member variables in the Inspector, 
 //if it happens to get used as a public variable 
 //in a script somewhere... such as this one!
 //(A "Serializable" member variable is any class
 //or primitive type that Unity can show in the 
 //inspector. Eg, classes include Rigidbody, 
 //GameObject, Texture2D (anything inheriting from 
 //Object) and primitive types include int, float, 
 //string, and enum.
 [System.Serializable]
 public class MyPairs {
     //NOTE: this class does NOT inherit from MonoBehaviour like 
     //scripts do by default! This just holds pairs, so won't need 
     //any of MonoBehaviour's methods like Update(), Start(), etc
     
     //Here are the variables you want to store in 
     //each element of the array. You can add as many 
     //variables as you want here.
     public GameObject myGameObject;
     public Vector3 myVector3;
 }

 //Here's the actual class this script was made for (so the
 //script should be called MyScript.cs)
 public class MyScript : MonoBehaviour {

     //Since we've made the MyPairs class "Serializable",
     //this array is now able to be shown as a variable in 
     //the inspector, and able to have its values saved 
     //when you save in Unity.
     public MyPairs[] arrayOfPairs;
 }

Now when you access arrayOfPairs[i] for some int i, you can use arrayOfPairs[i].myGameObject and arrayOfPairs[i].myVector3 to get the GameObject and Vector3 you want paired together.