Starting from the homepage, there is a box that says "site navigation." In that box, click "forum," then scroll way down towards the bottom and you will find classifieds. If you are selling a truck then make your ad under "trucks." You will need to put an actual price and not just a story about how much you refuse to take for it.
This rcsb thread is my favorite thread. Just about everyone here in the rcsb thread has built a rcsb truck, I think we all have a good understanding of what your truck is. I had a nice 6.0 shorty and recently sold it for $10k. The 6.0 buyer in general is looking at a 6.0 bc it's cheaper than the newer trucks.