Sox & Martin's SS-2 Duster was not a Pro Stocker if you are referring to it. SS stood for Super Stock. Not the regular Stock Eliminator but IHRA's heads-up version of it, a Jr. Pro Stock.. Ditto AHRA. And the number next to it designated it Super Stock 1, Super Stock 2 and Super Stock 3 (SS-1, SS-2 & SS-3) along with AHRA's similar GT-1, GT-2 and GT-3. They were all heads-up eliminators, i.e., no handicap start, same as Pro Stock.

SS-1 and GT-1 were for cars with big block engines (e.g., 427 cu.in.), SS-2 and GT-2 were for cars with medium displacement engines (e.g., 350 cu.in.) and SS-3 and GT-3 were for cars with small cubic inch, small block engines (e.g., 302 cu.in.).

If I remember correctly, the SS-1 and GT-1 cars were allowed multiple carburetion, the SS-2 and GT-2 car were limited to a single four barrel and the SS-3 and GT-3 cars were only allowed a two barrel carburetor.

What led to the the demise of these heads-up categories were a handful of cars (like Scott Shafiroff's Camaro below) that eventually dominated these eliminators. Same old drag racing story, man with the biggest bucks and/or best brains rules the class.