I'm pretty sure it was. As a young 'un spending the summer up in Bellville, I know for sure that Austin had AT 40 on K-98 (on FM!). Dallas was 1190 KLIF, and San Antonio was 55 KTSA. Why I'm struggling with the hometown, I'm not sure. 99.9% sure it was KILT. KNUZ was already "Country Fresh" by the mid 70s when I first started playing with the dials, and 79 was AC by the mid 70s, as well. It HAD to be KILT.
Edit to add: IIRC, Galveston had AT 40 on one of its two AMs as well, and I believe it was on the old "Big 14" KILE (now Radio Amistad)