If you want to go bigger you could use either a VN (or similar) commodore diff as they are cheap and plenty of different ratios, axles and have decent size discs on the back. Needs change of stud pattern.
Series 3 bluebird diff very cheap, same stud pattern, big axles and discs, i don't know how strong they are, but they are alot easier to fit than a commodore diff.
Or for a super strong diff you could go a Hilux item but they are heavy (like the commodores) and only have drum brakes and negate a stud pattern change.

An H165 from a B120 ute is what your after, they're the right width and are an easy transplant. Rumour has it they'll take 300hp which is plenty.

Ratio wise, well really depends on the track/circuit but the a good starting point would be the standard ratio ex the ute which is 4.111:1 and go up or down from there .....

Howdi all........

Wondering if anyone can give me some ideas about diff's and ratio's that would work good for track work. CA18 is the making the grunt, turning the shaft is a Quaife 5 speed with straight cut gears (ratios are pretty much standard) but cant seem to settle on what rear end set up is going to turn the black round things ?????

Any Ideas ?????????

Cheers
Peddler