T350 Diff change,what model??

[astonman]

Hi,I want to change my diff, currently 3.46 Hydratrac for a 3.91Quaife.Its a May 2005 T350.
I'd like to use all new parts.
Spoke to Topcats,but they couldn't source the new diff.
So,what diff am I looking for?
BTR M78 or M80 diff?

[astonman]

Thanks guys excellent recommendations.
Do you guys know what diff I'm looking for?
Cheers
Simon.

[astonman]

The cars 3.6, I want a CR box ( I hate the gap between 2nd and third in the standard box) and the 3.9 diff makes sense .
I want the ultimate fast road / trackable machine ( still using the 3.6).
I like the spring / damper set up I've evolved,which is Nitrons with 500lbs/inch front and 450lbs/inch rear,for the road.
I want a drive train to compliment this.last time I took the car out,we were late,and I noticed a significant issue with one black line and not two, with the Hydratrac.I don't think it's really up to very determined driving?
I have experience of ZF style locking diffs, is the quaife too tame?

[astonman]

Which diff case do I already have? M80 or M78. May 2005 T350.