Here in the state of New Hampshire, the last time I looked at their law on Street Rods (you can get a Street Rod Plate that gives you leeway on inspections), They classify a Street Rod as a vehicle manufactured before 1949 or a reproduction vehicle (kit car) that represents a pre 49 vehicle.

To Me based on Ford and Chevy, 1949 was the beginning of the modern era with front independent suspension on the passeger cars.

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Dan

63 Futura
59 F100
40 Ford PU
39 Ford PU