Mk1 or Mk2?

Mk1 tunnel with a pronounced hump on top of the tunnel round the gear lever: (MGBs Made in Australia)

Non-OD on the left, OD on the right: (Clausager)

Mk2 tunnel is wider with a flat top, with the lever in the same position on both OD and non-OD: (Clausager)

A 4-synch gearbox can be installed in a Mk1 car but the large removable panel on top of the tunnel needs a section inserted to move the hole back for the 4-synch gear lever, as indicated by the arrows: