Mazda MX5 gearbox for MGA

In the near future (not at time of this writing), the Mazda MX5 gearbox will be available for transplant into the MGA. It is already available for MGB. It will be provided by Vitesse Global Ltd, of Hinckley in Leicestershire, England.
For details from Vitesse see
http://vitesse-ltd.com/how-mazda-gets-the-classic-british-sportscar-into-gear.

Addendum, October 2017:
The Vitesse 5-speed gearbox is now available for MGA:
https://www.vitesse-ltd.com/products/mga-5-speed-mazda-gearbox-conversion-kit