"Bombs" and Lowriders are two separate styles. Typically, "Bombs" are late 40's - early 50's Chevys with 1954 being the usual cut off year. They concentrate on ALL original power plants, body styles and looks, with a hunger for OEM accessories to spice up the mix. They may or may not ride low. Lowriders are about flash and chrome and of course, ALWAYS ride low. Body and engine swaps are allowed. Sometimes the two styles mix, but not often. Google the Hispanic car culture in Southern California, following WWII.