Porting modules from OSC

I'm in the process of porting a module from OSC, and while i understand the information on the WIKI about required code changes and what is necessary to add OSC mod code to existing Zen Cart files, the structure of OSC leaves me scratching my head slightly. I have noticed that OSC seems to have a huge amount of files in the 'catalog' folder, that are not present in the top level of Zen. I have also noticed that OSC do not have an includes/templates type system. This creates a few problems when it comes to working out where i need to place ported files, or even which of the Zen files i need to look at to add the module code. For instance, the module i am currently looking at has product_info, shopping_cart and index files in the 'catalog' folder, where as Zen only has index in the top level folder. Now i'm assuming that the OSC index file has the same function as the Zen index file, and therefore any module code in the file needs to be added to the Zen index.php file, but as for which file in Zen is equivalent to the product_info.php and shopping_cart.php files is more of a mystery to me. Logic says it will probably a file somewhere within includes/templates, but i am uncertain about this.
I have also noticed that OSC does not have a folder called sideboxes, but instead one called boxes. I'm assuming this is the same idea only with a different name.

So, what i am looking for is some general information on how the structure of OSC relates to the structure of Zen so that i can locate relevant files that need to be modded.

Thanks in advance for any info.

Regards
Steve