Multiple TextBox to Array

It sounds like you want to create an object to store all the data in.

public class Vehicle {
   public Vehicle(string make...) {
       Make = make;
       ...
   }
   public string Make;
   public string Model;
   public string Year;
   public string Color;
...
}

Then you can use a List to store all vehicles, it will handle the size of the array for you:

List<Vehicle> Vehicles = new List<Vehicle>();
Vehicles.Add(new Vehicle(textboxMake.Text, ...));

And access them like:

textboxMake.Text = Vehicles[0].Make;

I agree with bwoogie - use a strongly typed object for this, and use a list if you can. This sample shows how to add a new vehicle when the user fills out the form and clicks a button. It has samples in there for either an array or a list. Note that both the array and the list can be passed into the same method, which expects an array of vehicles:

// you should be able to use a list...
List<Vehicle> list = new List<Vehicle>();

// or if you must use an array
Vehicle[] array; // initialize it like you do in your example
int arrayPosition = 0;

private void button1_Click(object sender, EventArgs e)
{
    // create an instance of a strongly typed object using your textboxes, etc.
    Vehicle v = new Vehicle();
    v.Make = textBoxMake.Text;
    v.PurchaseDate = dtpickerPurchaseDate.Value;
    v.Engine = comboBoxEngine.SelectedText;

    // add the strongly typed object to a list
    list.Add(v);

    // or if you must use an array
    array[arrayPosition] = v;
    arrayPosition++;

    // you can call a method that expects an array even if you are using a list
    DoStuffWithTheArray(list.ToArray());

    // or if you must use an array
    DoStuffWithTheArray(array);
}

private void DoStuffWithTheArray(Vehicle[] array)
{
    // expects an array of vehicles, but you can call it with a list or an array.
}