Using the internet and looking at what they do across the pond with their MX5 locosts makes sense to me.
Try here
www.locostusa.com/forums/index.php or
www.cheapsportscar.net by Keith Tanner who wrote the book " How to build a cheap sports car " Like Big Vern he has Mazda experience, it's free information, simples.
Assemble the diff as Mazda intended filling the holes in the outer rubber mountings with shoe goo ( available in the uk on ebay £6 posted ) to stiffen the mounts. At the front they use a small metalastic bush to locate the nose and keep the whole unit flexible and control vertical movement.
I am not an arm chair expert just an engineer for over 35 years using common sense and information that is already available, Hey but what do i know
Happy Days ................when it stops raining.