swapping to 911 control arm, because of these torsion bars Options

[Jetsetsurfshop]

I picked these up second hand and wondered if a stock 911 would use torsion bars this big. I assume that there Porsche parts because of the part numbers stamped on the ends.
I also noticed that one was stamped for the right side, the other isn't stamped. Should I assume that the unnamed one is the left?
The car is a dedicated track car and I've been using the stock 914 bars. Time to beef up the suspension. (IMG:style_emoticons/default/driving.gif)

[Steve]

Both the 914 and 911 control arms support 21,22 and 23mm torsion bars. The only advantage of 911 control arms is the stock torsion bar is 18.8mm versus the stock 914 torsion bars i think are around 17. Most people upgrade both types to 21mm for street and autocross. Typically only dedicated track cars use 23mm. I tried 23mm torsion bars with my 914-4 control arms and it rode like a rock. I switched back to 21mm.