Thanks for all the info
I will put the pinion assembly together and put it on the Mitchell drive shaft and adjust the preload by hand as told here because I haven't got an inch-lbs torque wrench. And then mount it in the banjo. It is possible that the preload in my set up was not correct because the second lock nut was loose when I took of the torque tube. I did not notice anything wrong with it when I drove the car, it wasn't noisy or anything so!
Hope everythings turns out OK, I also put in a syncro trans from Mitchell in my coupe. I have a touring engine in it also. I have the stock 3.78 gearing.
Thanks,
Eddy