[vidguy]

It's a business choice how you present your information to your users, but I must say having too many categories can make finding items difficult.. I personally prefer searching, and not only on your site. If you have "search", make it useful.

Searching can be made much more effective by including phrases, words, or numbers that are obviously related to the product within the record for that item.. Metadata..

If all you have from the data from your supplier is Rad Cap.. Add to the description "radiator" or other words that make sense to someone looking for it...

If you are saying that for example, the 1972 Pontiac A Body Radiator Cap you sell is called "Rad Cap" in the bit of data you get from your supplier, and you take the data you get from the supplier and simply insert that into the items' record in your Database, then I think that's not the best practice. There is a lot you can do to add useful information.

In my business, we deal with thousands of records in many databases for a variety of purposes. I do understand the effort. But as I said it's a toss up.
We can all improve our web presence, but that's the beauty of the web, You CAN change it all the time. Not like a Catalog..