It could be true, but like a lot of things about Billy, some have been enhanced over the years. I remember hearing (I didn't see the show) that when Jimi was on Johnny Carson, he was asked about who he listened to and Jimi said there was a cat from Texas, named Billy Gibson, that he liked. Easy to understand him mixing the name up.
Besides creating a thousand catchy licks, Billy has crafted a thousand different tones with amps and effects. Also, I think Billy doesn't get much credit for his singing. He has as many different sounds as he has amp tones.
If you can keep your feets still listening to this, get help:
http://www.youtube.com/watch?v=y1-q6WHxA4E or search you tube "ZZ Top Chevrolet Largo Maryland".
I am living just a few miles from the 'Simonton' and "Cinco' (Cinco Ranch) and The Red Brazos River land mentioned in the song and I am about three blocks from the highway where they "hit that freeway at sunset"
Frank has been criticized for not being a good drummer, but check him out about 2:10 in the clip.
Pearly through a dimed Marshall, doesn't get much better.
Six Pack is a pretty good survey course for the early stuff, but it lacks anything from Deguello because the lawsuit was pending still when it came out. Also it (6PK) was remixed with too much reverb and electronic drums. Compare Just Got Back From Baby's in six pack to the original and see if you don't agree.