Ok well I've gotten a hold of a VN Calais V8 diff with LSD... so im after some diff gears to shove in while im changing diffs...

I know the ratio I want, 3.73.

But my question... Should I buy them new, get them from a VZ SS manual and pay almost new prices or get them dirt cheap out an R31 auto skyline?

Will there be any issues with diff gears from a car that old? I know they fit... but will they make noise or whine or anything? What sort of lifespan to diff gears have?