Complex sentence: The characteristics of the rat rod style of hot rod and custom cars, imitating the "unfinished" appearance of some hot rods in the 40s, 50s and 60s.
Split into simpler sentences: The characteristics of the rat rod style of hot rod and custom cars. Usually imitating the appearance of being "unfinished" known of some hot rods in the 40s, 50s and 60s.