Probably the same way you'd go about putting any diff in a 1200 that isn't a direct bolt in.

Basically, you'd have to cut off all the old mounts etc that aren't to be used and weld on things suck as spring perch's, brackets and the like depending on what car the diff came out of.

I would suggest a Hilux diff with an LSD centre. A lot of hi-po cars use these with great results as they are very strong and light. You could even strengthen things up a bit by cryo treating and/or shot peening the axles etc should reliability become an issue.

I too thought about the 9 inch, but it kinda defeats the purpose of having a nice light car with a powerful engine when the diff weighs so much.

Feel free to correct me of i'm wrong here!