Jimi Hendrix and Billy Gibbons jammed back at the hotel a few times when they shared bills (The Moving Sidewalks opening for The Jimi Hendrix Experience).
It made enough of an impression on Jimi that when he was on the Tonight Show and asked which up and coming American players he liked, he said Billy Gibbons.

Here's a link to audio snippets of Billy Gibbons' Moving Sidewalks:
All Music: Moving Sidewalks : Songs
99th Floor was their big "pop" hit, but the Flash album was more blooze jams and psychedelic riffs.

The original lineup of ZZ Top did not consist of Frand and Dusty (from Dallas' American Blues), instead there was another member of the Moving Sidewalks in the lineup. And it was heavy.
Check out "Salt Lick" for a taste of the original ZZ Top sound.
All Music Guide : ZZ Top : Songs (page 2)
"Miller's Farm" was the flip.
ahhh yes...”make out parties” in the 8th grade with “Moving Sidewalks, 13th Floor Elevators, etc” on the turntable, good memories now that someone awaoke them in me, thanks.
IIRC, they were in a high school battle of the bands or at least came to play in 1969 or 1970 in Houston, too foggy.
I saw ZZ Top live in Corpus, 1983? aftre sharing a bottle of CAPT. Morgan and other dry goods, they were great live!
They sounded really good from the floor of the bathroom.