Looks like I'm off to Singapore for work for the next couple of weeks. I'll be away from my wife and my 3 year old daughter for probably the longest time since she was born.
I also won't be able to work on the Cobra for a while
I picked up a 3.9:1 ratio Hydratrack diff from a HSV GTS300. I'm going to adapt it up to the AU Ford IRS. I've been doing a fair bit of research into this and I'm pretty sure I can do it with a minimum of fuss. The Hydratrack LSD center is a bit more progressive than most LSDs it uses a viscous coupling to link the two axles. This makes it speed sensitive rather than torque sensitive. As one wheel slips the vanes in one half of the unit turn in relation to the other. This builds up hydraulic pressure much like a torque converter and forces the other half to catch up. It doesn't give the sudden engagement that lockers and regular clutch or cone LSDs do so hopefully won't be so quick to enduce power oversteer out of the corners. They are used by TVR in their cars and AC used to use them in their Lotus V8 powered Cobra.
Cheers