Hi mate, the imports have shorter gearing so won't work with uk diffs/driveshafts, so you'd need to find one that has the same ratios, not sure if there are uk boxes with the same as imports, best off asking savage on that one.
Theres a guy in Hebden Bridge that does rebuilds & swaps ill see of I can find his number, if I remeber it was about £ 350.
You been running round without a rear wing a couple of weeks ago ?