Essentially gearboxes go with engines, in that the choice of engine limits the choice of gearbox. Here are the chief options:

MGB Gearbox, fitted to B series engine – normally aspirated or super charged
This is a strong, if bulky ’box with a tight gate and 4 speeds. Normally it comes with an over drive unit on third and fourth. This in effect gives 6 speeds, if you are more co-ordinated than me!! Over-drive third is ideal whilst waiting for the opportunity to over take. Flick the switch and go.

Rover LT77 Gearbox, fitted to Rover V8
This is another strong ’box, with five speeds. It is great in rear wheel drive format as in the Rover SD1 and TR7. It met its match behind a torquey diesel in a Land Rover.

Rover R380 Gearbox, fitted to Rover V8
This ’box is rare in two wheel drive format, most having been fitted to Land/Range Rovers. It is a great box to go with the 3.9 EFi V8.

Ford Type 9 Gearbox, fitted to B or K series engines
The MGB ’box is not exactly in the first flush of youth! If you want five speeds from a compact ’box, bellhousings are available to match the Type 9 to the B engine and indeed to the K series engine.