Special ordered cars

V may just signify Valiant. As all Plymouth A body cars are a Valiant. Just like the Demon is technically a Dart.

The S code is just high price range, regardless of factory selected, dealer selected or buyer selected options. All Dodge Chargers, for instance, were Hamtrack build cars because the body required different sheetmetal stampings that were not shared with other plants. Dodge had the Charger as an exclusive body, while Plymouth had the Barracuda as an exclusive body, during the campaign changeover in '67-'68.

Chargers got the XS vin, because it is a high price range car. I would imagine a VS just signifies model + price range. In 1970, the Barracuda was no longer in the A body/ compact line and it marked the very first year for the Valiant Duster body, which carried the torch for the compact sport model cars in 1970. Dodge didn't get a coupe model until the 1971 marketting campaign changeover with everything. The Dodge coupe followed, due to the good sales reported from the Chrysler/Plymouth dealerships. They wanted to sell coupes at the Dodge dealerships.

This is also why you couldn't buy a 1971 Dart Swinger with a 340 from a Dodge dealer's lot stock. It had to be ordered at that point, because the 1970 year was sort of a fluke. They kept the hardtop with the 340 that year, because they didn't have a coupe available in 1970. From 1971 on, if you wanted to buy a high performance compact from Chrysler/Plymouth or Dodge lot, it was a coupe body.

With that said, seeing as how in 1970, the Valiant Duster was Plymouth's exclusive body for that one year, that may explain the VS vin. Makes me wonder if all 1970 Dusters have this vin.