MiniMatic Differential
In Australia there was only ever one diff ratio in auto boxes. It was about right for a 998cc 700kg Mini on 10" wheels or a 1098cc or 1275cc.
A 1275cc auto mini with 10" wheels (or later 12" low profile tyres which are roughly the same outside diameter) will be undergeared and will be quick off the mark, but noisy at motorway speeds.
Manual diffs won't fit auto gearboxes.