There has never been a Ford Mustang station wagon, but there have been many conversions done on the aftermarket. This particular one combines a 1967 Ford Country Squire roof with what appears to be a 1968 Mustang Coupe.
Under the hood is a 302 engine with an Edelbrock four-barrel carburetor and an Edelbrock Torker 302 intake manifold. The rebuilt motor has about 9,000 miles on it, according to the seller.
Alas, the bidding has ended on this car, but it's worth a look at Ebay just for the pictures..