I did notice the machined caps on the Merc (very cool, by the way!), and in most cases those would be enough to rule it out as a purely box-stock model. The plug wires on the Chevelle may be a deal breaker for a box stock entry, but again, kind of depends on the show. Should be no problem at all on the Ram.
If it were me? I'd just enter them all in the 'custom' class. Better still, I'd just show them, and not enter them in the judged competition at all!