|The MGA With An Attitude
TIRE CARRIER, Modified Standard Rack #2 - AT-102O
This one looks very simple, a standard factory type luggage rack with the rear bar bent rearward a bit. So far I don't know what is used to secure the wheel to the rack.
You may notice with any boot lit spare tire carrier it is best to position the tire as far back as possible to be low to not obstruct the view from the rear view mirror.
Something similar on an MGB, with a better rear view: