7 degrees is excessive, the only modern vehicles equipped with radial tires that uses that much caster are the old solid axle Jeep Grand Cherokee, Grand Wagoneer, and the Wrangler, all with coil spring suspension. Most of the vehicles I've seen where a 7 degree caster angle is suggested are lightweight, short wheelbase cars, like T Buckets or Model A roadsters.
I would suggest rechecking the preload on the tie rods. They may seem "tight", but if the preload isn't correct, they will "loosen up" when driving, causing a toe out condition. The same goes for the drag link, if it is still the type with the serviceable ends. The preload setting isn't hard to do, simply remove the cotter pin, crank the plug in until it seats, then back it off to the first cotter pin hole. You will need a Drag Link socket, which is more or les a larger screwdriver bit with a 3/8 or 1/2 inch square drive on it. You may have to get ahold of a Snap-On, Mac, Matco, or Cornwell dealer to get one if you cant find one at the parts store.
