[400TT]

That's a good suggestion Mike and would work better, but would mean new rear wheels as Commodore diff is wider, let alone changing stud pattern etc. Plus diff would require quite a few mods to fit. There is a Commodore diff up here in a 347 stroker DRB, does heaps of km's and regular track and strip work(low 12's) and is holding up fine...so far. And yes, it's another Warrick build from eons ago.

Another thing to keep in mind is that I reckon 9" would help re-sell value and of course brag value. Keeps an all Ford drive train. You can't beat range and availability of 9" parts...the amount of bargain 9" stuff that I have walked past at swap meets.

Finding a 2nd hand Torana 9" would be cheapest and easiest option I reckon...but not necessarily the best, depends how you look at it.

Also I wouldn't bother doing diff swap without going LSD as well.