The project, which was first announced in September, is expected to focus on the rivalry between the Ewing brothers.
TV Guide says that original cast members Tilton and Kanaly have now agreed to reprise their roles as Lucy Ewing and Ray Krebbs in the pilot.
They will join Patrick Duffy, Linda Gray and JR Ewing, who have already signed up to return.
Tilton had previously admitted that she wanted a role in the show, describing the script for the pilot as "absolutely wonderful".
TNT's Dallas will also star Brenda Strong, Jesse Metcalfe, Julie Gonzalo, Josh Henderson and Jordana Brewster. Filming for the pilot is expected to begin in Texas in late April or early May.