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

Non-OD on the left with the lever at the front of the oval rim ring, OD on the right with the lever at the rear of the trim ring: (Clausager)

This shows how easy it is to access the OD (yellow arrow) and reverse light (green arrow) switches by removing the large panel on top of the Mk1 tunnel (G Lai):

Note this is the early 3-synch box that does not have provision for a reversing light switch, the smaller plug here in the same position has a different thread and is part of the reverse gear detent.

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

Mk2 has a small removable panel HZA1431 screwed to the tunnel:

Removed - suppliers show gasket AHC188 under it and I did find that on a 78 sitting on the metal tunnel but both Bee and Vee have thick insulation there which makes the gasket pointless:

Mk2 with the 72 and later centre console and arm-rest/cubby. What the rubber bit at the top of the gaiter is I have no idea, it came with the car - possibly hiding a bit of rattyness at the top of the gaiter, but like steering wheel and the gear knob it seems churlish to replace that part of the car's 'character':

With that the tunnel carpet can be cut to allow removal of the small access panel without pulling the carpet back, saving a section of carpet to drop back on top for noise insulation:

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: