It depends on who you are talking to. The purists pick a year and they can't use parts manufactured later than that year. On the other hand, most rat rods are a collection of old scrounged parts. It's a fun challenge and they are fun cars. We had an old lakes racer living around here and he built one. Remember the flathead with 3x2's with the fuel block that had the clear red or blue hoses running to the carbs? Stromberg 97's were the best. Anyone that built back then remembers those explodo cars fondly and they are a kick to drive.