add globals for indexer :) works now...

modify_csv_exporter.php

<?php
/**
 * Plugin Name: WooCommerce Modify CSV Exported file
 * Description: Adds and removes desired and undesired fields respectively
 * Version: 1.0.0
 * Author: Ray Flores
 * Author URI: http://www.rayflores.com
 * Requires at least: 3.9
 * Tested up to: 3.9
 *
 *	License: GNU General Public License v3.0
 *	License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */
 $GLOBALS['wc_csv_export_index'] = 0; 
 //  add reverse order to orders by order number, as they are exported.  
function rf_wc_csv_add_query_args( $query_args) {

		$query_args += array(
				'orderby' => 'date_query',
				'order' => 'ASC',
			);
		return $query_args;


}
add_filter( 'wc_customer_order_csv_export_admin_query_args', 'rf_wc_csv_add_query_args', 10,2);
// set the data for each for custom columns
function rf_wc_csv_export_modify_row_data( $order_data, $order, $generator) {
		

		foreach ($order as $cust_data) {
			$custom_data['cust_num'] = $GLOBALS['wc_csv_export_index']+1;
			
		}
	
	foreach ( $order->get_shipping_methods() as $_ => $shipping_item ) {
		if ($shipping_item['name'] == 'International') { 
		$custom_data['shipping_method'] = "INT"; 
		} else {
		$custom_data['shipping_method'] = "RG1";
		} //endif
	}
	$i=1;
	foreach ( $order->get_items() as $item_key => $item ) {

			$product = $order->get_product_from_item( $item );
			$sku = $product->get_sku();
			$custom_data["item_{$i}"]  =  $sku;
			$custom_data["item_{$i}_qty"] =  $item['qty'];
			$custom_data['order_number'] = preg_replace('/[^\p{L}\p{N}\s]/u', '', $order->get_order_number());
			$custom_data['source_code'] = 3;
			$custom_data['payment_method'] = "I";
			$i++;
	}
	while ( $i < 6 ) {
		$custom_data["item_{$i}"]  =  '';
		$custom_data["item_{$i}_qty"] =  '';
		$i++;
	}

/*
		'item_1' => $item['name'],
		'item_1_qty' => $custom_data["item_{$i}_qty"] ,
		'item_2' => $item['name'];
		'item_2_qty' => $custom_data["item_{$i}_qty"] ,
		'item_3' => $item['name'];
		'item_3_qty' => $custom_data["item_{$i}_qty"] ,
		'item_4' => $item['name'];
		'item_4_qty' => $custom_data["item_{$i}_qty"] ,
		'item_5' => $item['name'];
		'item_5_qty' => $custom_data["item_{$i}_qty"] ,
		'cust_num' => '',//$this_num,//$cust_num,
		'payment_method'       => 'I',
		'source_code'       => 3,
		'billing_first_name'  => $order->billing_first_name,
		'billing_last_name'   => $order->billing_last_name,
		'billing_email'       => $order->billing_email,
		'billing_phone'       => $order->billing_phone,
		'billing_address_1'   => $order->billing_address_1,
		'billing_address_2'   => $order->billing_address_2,
		'billing_postcode'    => $order->billing_postcode,
		'billing_city'        => $order->billing_city,
		'billing_state'       => $order->billing_state,
		'billing_country'     => $order->billing_country,
		'shipping_first_name' => $order->shipping_first_name,
		'shipping_last_name'  => $order->shipping_last_name,
		'shipping_company'    => $order->shipping_company,
		'shipping_address_1'  => $order->shipping_address_1,
		'shipping_address_2'  => $order->shipping_address_2,
		'shipping_postcode'   => $order->shipping_postcode,
		'shipping_city'       => $order->shipping_city,
		'shipping_state'      => $order->shipping_state,
		'shipping_country'    => $order->shipping_country,
		'order_number'        => preg_replace('/[^\p{L}\p{N}\s]/u', '', $order->get_order_number()),
	);
 */
	if ( 'default_one_row_per_item' === $generator->order_format ) {

		foreach ( $order_data as $data ) {
			$new_order_data[] = array_merge( (array) $data, $custom_data );
		}
	} else {

		$new_order_data = array_merge( $order_data, $custom_data );
	}
	$GLOBALS['wc_csv_export_index']++;
	return $new_order_data;
}
add_filter( 'wc_customer_order_csv_export_order_row', 'rf_wc_csv_export_modify_row_data', 10, 3 );
 
 
// set order columns
function rf_wc_csv_export_custom_order_columns( $column_headers, $generator ){
		if ( 'default' === $generator->order_format ) {
 
		$column_headers = array(
			'cust_num'                 => '',//CUSTNUM',
			'billing_last_name'               => '',//CUSTOMER LAST NAME',
			'billing_first_name'             => '',//CUSTOMER FIRST NAME',
			'blank'                    => '',//BLANK',
			'billing_address_1' => '',//CUSTOMER ADDRESS 1',
			'billing_address_2'                 => '',//CUSTOMER ADDRESS 2',
			'billing_city'                 => '',//CUSTOMER CITY',
			'billing_state'				=> '',//CUSTOMER STATE',
			'billing_postcode'            => '',//CUSTOMER POSTAL CODE',
			'billing_phone'       => '',//CUSTOMER PHONE #1',
			'keycode'       => '',//KEYCODE',
			'po_number'       => '',//PO #',
			'shipping_method'            => '',//SHIP VIA',
			'blank2'                    => '',//BLANK',
			'blank3'                    => '',//BLANK',
			'order_date'           => '',//ORDER DATE',
			'order_number'        => '',//ORDER NUMBER',
			'item_1'            => '',//ITEM 1',
			'item_1_qty'     => '',//ITEM 1 QTY',
			'item_2'            => '',//ITEM 2',
			'item_2_qty'     => '',//ITEM 2 QTY',
			'item_3'            => '',//ITEM 3',
			'item_3_qty'     => '',//ITEM 3 QTY',
			'item_4'            => '',//ITEM 4',
			'item_4_qty'     => '',//ITEM 4 QTY',
			'item_5'            => '',//ITEM 5',
			'item_5_qty'     => '',//ITEM 5 QTY',
			'shipping_last_name'	=> '',//SHIP TO LAST NAME',
			'shipping_first_name' => '',//SHIP TO FIRST NAME',
			'blank4' 		=> '',//BLANK',
			'shipping_address_1' => '',//SHIP TO ADDRESS 1',
			'shipping_address_2'	=> '',//SHIP TO ADDRESS 2',
			'shipping_city'       => '',//SHIP TO CITY',			
			'shipping_state'      => '',//SHIP TO STATE',
			'shipping_postcode'   => '',//SHIP TO POSTAL CODE',
			'payment_method'       => '',//PAYMENT METHOD CODE',
			'blank5' => '',//BLANK',
			'blank6' => '',//BLANK',
			'blank7' => '',//BLANK',
			'blank8' => '',//BLANK',
			'blank9' => '',//BLANK',
			'blank10' => '',//BLANK',
			'blank11' => '',//BLANK',
			'blank12' => '',//BLANK',
			'billing_email'	=> '',//CUSTOMER EMAIL',
			'billing_country' 	=> '',//CUSTOMER COUNTRY',
			'shipping_country'    => '',//SHIP TO COUNTRY',
			'billing_phone_2'    => '',//CUSTOMER PHONE #2',
			'shipping_phone'    => '',//SHIP TO PHONE #1',			
			'shipping_phone_2'    => '',//SHIP TO PHONE #2',
			'blank13' => '',//BLANK',
			'blank14' => '',//BLANK',
			'blank15' => '',//BLANK',
			'blank16' => '',//BLANK',
			'blank17' => '',//BLANK',
			'source_code' => '',//SOURCE CODE',
		);
	}
	return $column_headers;
}
add_filter( 'wc_customer_order_csv_export_order_headers', 'rf_wc_csv_export_custom_order_columns', 10, 4 );

function rf_wc_remove_column_headers($csv){

		$first_line = strpos($csv,"\n");
		$csv = substr($csv,$first_line+1);
		return $csv;	
}
add_filter('wc_customer_order_csv_export_generated_csv','rf_wc_remove_column_headers', 10, 4);