To follow up on this project, I've uploaded the files and ran the SQL updates. However, there's a few problems that I suspect are easy to fix but beyond my knowledge. I'm not seeing the subheads appearing which is a result me not doing it right or lacking a proper file merge.
For the purpose of seeing my pages with Cat ID's and product numbers, we'll use a random product page on my site. To avoid search engine discovery, I've obfuscated the domain name…
http://www.DOMAIN.com/index.php?main...ndex&cPath=290
(change domain to R U G G E D R A D I O S)
Since my use for this mod is for the product listing page only, I only edited line 10 in the "defines" file which is what I think I'm supposed to be doing, right? Since this is new territory for me and other Zen Cart users, this also begs the next question. Once the files, code, and upload are all accurate, does this mod automatically move product down to fall under the subheads? See image for better explanation:

Here's the defines I'm using for that:
Code:
<?php
//Category or Product Listing Subheadings (t=100211)
//=================================
//includes/languages/english/extra_definitions/your_template/listing_subheads_defines.php
// Listing Subheadings by Glenn Herbert (gjh42) v0.9 test 2011-12-16
// comment out any defines not to be used
define('CAT_SUBHEADS', serialize(array(9=>'Subheading for Cat 9',23=>'Subheading for Cat 23',45=>'Subheading for Cat 45'))); //replace 9, 23 & 45 with cat ids; duplicate items as needed - escape apostrophes \'
define('PROD_SUBHEADS', serialize(array('290_660'=>'Sample text above 1st item with Prod ID of 660','290_661'=>'Sample text above 2nd item with Prod ID of 661'))); //replace 2_20_23 & 22_16 with cPath+_+prod ids; duplicate items as needed - escape apostrophes \'
define('CAT_COLUMN_DIVS', serialize(array(9,23)));//cats to start new cols - must be subheads
define('PROD_COLUMN_DIVS', serialize(array('7_57','22_16')));//prods to start new cols
//EOF
In a private message, you referenced that you weren't sure if I had a proper merged file and that maybe your live version is different than the beta file I tested. I wouldn't know, but maybe the link above will allow you to see something obvious.
Thank you for this!