So I contacted numerous people regarding the diff problem.
I think I have the issue solved thanks to Russ at FWM. I am picking up another gear tomorrow which should* fit
Today I got the Diggity Designs Carbon upper decks which I have been expecting. They came from the US within around a week, which isn't too bad.
here they are, all installed:
They look awesome, and the chassis is now much more rigid.
All i'm waiting on now is that crown gear and I should be up and running again.
Will report back tomorrow.