Look for the "donations" tab, between the calendar tab and the downloads tab, and make your donation there. The minimum I believe is $20. I'm not sure that this is the best place to sell such cars though. They look very nice, albeit totally stock (this site is dedicated to modified Z cars). The Z would be more appropriate here, not sure about the wagon. I think you might be better off trying to list them on http://bringatrailer.com/ as I think you're more likely to find the right kind of buyer there.
You may also want to check out the https://www.classiczcars.com/ forums, as that site is geared more to stock cars/restorations.