OK, cranky old guitar purist two cents here...rockabilly is a very primitive sound, and a pod, or a modeler, or a digital amp, or any of that stuff is going to give you an approximation at best. What you need is a small tube amp, and a slap back delay (preferably tape, but who can afford 1000 bucks for an echo?) and the guitar of your choice...those cats used teles, strats, Les Pauls, cheap pawnshop stuff...whatever they could afford...it's a big mistake to try and spend alot of dough on modern gear to try and get a sound that was made on the cheap for the most part.

Ladykillers load dice on me, behind my back while imitators steal me blind