Came across this article about Cliff Gallup who you may remember playing for Gene Vincent.
This is what Hank & Bruce were listening to (amongst others of course) in the early years.
Of special interest is the echo machine used & the authors thoughts & techniques for getting "that sound" by using modern guitars & pups etc...
Could this indeed be part of the beginnings of "that sound"
http://www.rockabillyhall.com/soundlikecliff.html
Cheers
Dick.