Ping to SA's link to the large map for NASCO corridor.
Also, if you go to the Texas Department of Transportation, they likely will have information about the highways/freeways planned for expansion and those already having improvements made to accommodate for the corridor project.
The main highways that I am aware of right now are I-35 and I-29, going north. But there are other highways which branch off, east-west, from the main north-south artery.