Thanks everyone for your contributions.
Peter, you are quite right, the difference between the 11 and 11A is in the bearings which support the impellor shaft.
I am really gutted that the supercharger on offer is counter rotation.It would have otherwise been perfect.
From what I have read on a number of forums the Powerdyne blowers don't have a great reputation for reliability. I understand the impellor shafts were prone to flexing resulting with the internal belts snapping. I believe the 11A was a big improvement and helped to eliminate/reduce those problems.
On the positive side, I'm glad I looked closely into this supercharger ()spec before I placed a bid!!
Incidentally Peter, it's as a result of viewing some of your engine bay/supercharger images, that I was able to identify a difference to the one on offer!
I have considered the roots type charger, however I wanted to keep the engine bay as close to the Superblower spec as I reasonably could on my own car.
I don't think re-pulleying all my assessories would be feasible or a cost effetive option.
The Powerdyne's fitted to the Superblowers are mounted in such a position they are very close to the engine bay/wing (fender) edge.
As such, any change in the mounting position may result in the supercharger either no longer fitting into the engine bay or not aligning with the throttle body hose.
There seems to be a number of issues I can think of if I were to try to modify the counter clockwise blower to make it a clockwise blower. I think it would need a different impellor(opposite curve on the vains), also the outlet counter-clockwise spiral casing would need replacing with a clockwise spiral. And of course where the outlet is positioned has to be right to pick up the hose to the throttle body. After such modifications, I think it would need to be professionally re-balanced etc.
I think I'll keep my eyes open for another 11A Powerdyne; clockwise rotation and ideally - polished. If any of you find one, please let me know!!
Thanks all.
Gary