St. B, as Trailer said, even if you move the scope in the mounts, the eye relief will be the same. Most scopes sold these days have at least 3 inches of eye relief. Which is enough for all but the heaviest recoiling magnums!
Leupold and some other brands have 5 inch eye relief. More is almost always better, so get the best scope that you can afford, and with the most eye relief too. Leupold and Nikon make two of the best 200 +/- dollar scopes that you could buy!