Full specs (including dimensions) are available at blackberry.com. Key placement might be a bit different but I haven't compared the two myself. Potential fit issues are going to depend a bit on the case itself.
I'm using an 8700c case on an 8703e. If there is a size difference, it certainly isn't affecting the fit of this case, which is just right.
The Blackberry accessories store does list their cases for the "8700 series" which includes the 8703e. So it would seem that there is no form factor difference.