The only "Republican" seat back then was probably Craddick's Midland district, and it was a newly Republican district at that.
Yes - Craddick was one of the "Dirty Thirty" who took down Mutscher and Barnes. There were about a half dozen Republicans at the time - Walter Mengden and Bill Blythe of Houston, Jim Earthman of Galveston are the ones that come to mind. There were also two or three Republicans in the Senate - Hank Grover is the one that comes to mind immediately, because he was our nominee for Governor in 72.