I think you might struggle a bit to find a mazda diff with a 3.1 ratio which is what I am led to believe you will need to run a bike engine. It might pay to mongrel the back end to take the sierra diff.
yeah thats what i was thinking, although i wasn't keen on the idea as it may cause more problems if i ever decided to put a car engine in, which is why i was wondering if such as quaife make a suitable LSD i could fit?