Lots of issues here.

Firstly type 9 boxes are hopeless beyond 200bhp in std form. They will last no time at all on decent powered turbo motor!!!

We used to run a type 9 in our hill climb pinto powered sunbeam and we were usually lucky to get a race meeting from a std box! That said a suitable quaife type 9 soon sorted things out!!

However for your setup you have a bad mix of parts. The std type 9 will not fit the cossie flywheel and a cossie clutch will not fit a pinto flywheel.

When we went cossie powered with our quaife type 9 we went for a pinto size 9 bolt flywheel and 7 1/4 twin plate clutch.

If you keep with a std size pinto clutch your range is limited hence why I recommend the 7 1/4. We did briefly run an AP cover and 4 paddle pinto clutch but the 7 1/4 unit gave much cleaner and quicker gear changes.