Troy and Marc,
Another point to ponder. Since you do have a non-commercial posting policy maybe you could limit who and how things get posted. For instance if a member posts that he bought a whatchamacallit from XYZ Company and they treated him good a website link or address could be posted. Word of mouth referrals are the best form of advertising. General suppliers such as Chevymall or GMPartsdirect could be listed somehow.
I do feel however that a post that says "I sell such and such and you can buy from me" should be strongly controlled. You don't want this to become an advertising nightmare with vendors essentially getting free advertising. There are some ads that come up every so often in the forum like that.
Maybe limiting the posting to "supporting members" or "supporting vendors" only would help. Other thoughts??????
Although the idea of an aftermarket forum is great, I for one don't want to see pages of ads from people who don't contribute in other ways.