front Diff tech questions

Hi All,
I hope someone in here can answer a couple of off the wall tech questions.

I have a problem with the front diff on my 05 TRV. ( actuator and lots of miles)

I recently picked up a front diff from an 07 FIS 400 auto. It is complete and in excellent shape complete with axles and drive pinion assembly.

I would like to put this in my TRV - to gain diff lock and its easier than rebuilding mine.

My diff is 3.6:1 ratio as far as i know. and I think the 400 is 4.00:1 - I understand the ring gears are the same and cat used the pinion to change ratios.
First big question:
Can I just use the 10 tooth pinion in my old diff to make the new one it 3.6:1 ??

The axles that came with the 400 diff are in great shape but are the wrong end for my 05trv spindles/knuckles.

Second Big question:
Will the outer CV's from my 05 axles fit the 07 axles ( they are good shape)

FYI i am a mechanic and the work is not the problem - I just am not sure if the parts physically fit.
Thanks in Advance for all help.
Andy