Something that you have to keep in mind is that by design the leaf spring rear end already has a built in roll centre. By fitting a pan hard,watts, Mumford or other, a fixed point of roll centre doesn't magically appear. The built in rc will still be there but you will be working with or against it depending on were you set the height.
You will probably find that you end up very close to where silly old mr Datsun set it 40+ years ago. I would say he was a pretty smart bloke.
It is pretty easy to work out your rc, diagrams on google.

Is lateral location needed, probably not in such a light car.