Last week we featured an early Dodge van, and yesterday in this space was a Corvair Greenbrier from 1962. So it seems only fitting to follow up with one of these old compact trucks from the other member of The Big Three. But this one’s probably the rarest of them all — a 1961 Mercury Econolinepickup. That’s right — Mercury. Why, you may ask, was there such a thing? Well, it