Don, that's pretty much all wrong mate.
You 'MUST' have the same front and read Final Drive Ratios !!!!!!!!!
If you don't your centre diff will be Toast
Available Ratios for the TY754 and TY752 are 4.44:1, 4.11:1, and 3.9:1. The later is acheived in the JDM car by using 3.9 CWPs in both the front and back with 1:1 drop gears in the centre dif. Euro cars use a 3.9 in the front and a 1:1.1 drop gear, then a 3.54 (3.54 x 1.1 =3.9) in the rear. I think the reason for the difference is to lower the speed of the prop shaft on the euro cars with their higher top speed.
If you were using the box you got from Grieg, it has a 4.11 front diff from memory.
---john---