We deal with this issue all the time on the new car side with my company's shopping cart service. Early on we received (loud and clear actually) the consumer feedback, "that what exactly is it you want me to shop and buy online."
If it helps, here is the process we teach as part of our implementation. Most dealer services use an order-guide based product to explode VINs and tell consumers what each option code is.
The process to use in your dealership to handle stock ins is to make sure that the factory options per the invoice are entered. There are tools such as from VIN Solutions to facilitate capturing these for used cars.
What you have to be careful of are the exceptions (naturally). Here is the list we know of:
1) ADP has no field for exterior nor interior color codes. We have our dealers enter those two in the options field as the first two options on every vehicle and parse them out from there.
2) The EDS DMS now owned by ADP and used by all Saturn stores only has room for 4 factory options.
3) AutoSoft only has room for 10 factory options and their export tool doesn't allow the export of the trim code (although their CEO Charlie Prophet who I met at NADA last week has offered to correct this and automate the whole process for us)
4) Sometimes there are factory integration points to help with this. The industry standards organization run by NADA, known as STAR, has a standard around how this data is supposed to be structured and how to handle its interplay between the OEM and the dealer. Few OEMs have adopted it.
5) Reynolds is a better DMS than ADP for this since if you set it up correctly, you can get sub-option codes for packages and preferred equipment listings... but beware... some OEMs have implemented it correctly (i.e. Chrysler)... others have not (GM just uses text for the sub-option codes... text doesn't mean much to an order guide database). Where it is not an integration point, Reynolds also sometimes has a data service you can subscribe for so you don't need to build and maintain these tables manually... but beware... Reynolds takes shortcuts on the packages / preferred equipment groupings essentially making them useless to your web providers unless their service can look up the sub-option listings.
Which brings up the exact point to the concept we were launching at NADA for the OEMS who don't have one of their own...
A contextual, side-by-side comparison of trim level differences and options.
As the precursor to shopping online
Be an online consumer who wants to consider the Saturn Astra. Is a configurator going to help you with what you need to know to be comfortable shopping for your Astra? Would you leave the configuration process comfortable that you had the Astra you wanted? That a better choice wasn't available? What would you do in a configurator where you were flexible as to whether a car had a particular option or package that you wanted?
Think about that as the entry to consumers viewing your vehicles. What should your website look like if it was built to educate them so they could shop online (vs. send you an email inquiry)?