This plate is made to mate the MGB 1800 5-main bearing engine to an early MGA 1500 low starter gearbox (1955-1958).

The 18GB was the first 5-main bearing MGB engine mated to the MGB 3-synchro gearbox in 1965-1967 (before introduction of the 4-synchro gearbox in 1968). The 18GB engine used a small diameter (10-inch) flywheel with 120-tooth ring gear, and pilot diameter and bolt pattern to fit the 5-main bearing crankshaft. Using this (18GB) flywheel (1965-1967), you can mate any MGB 1800 5-main bearing engine (1965-1980) to any MGA or early MGB (pre-1968) 3-synchro gearbox. The "trick" is that you need an engine rear plate that matches the bell housing bolt pattern.

This rear plate will fit the early MGA gearbox (low starter models), and includes center bore size to use the rubber rear seal needed for the 5-main bearing engines. It may also be used to install a 5-speed gearbox (with 5-main engine) if the 5-speed gearbox is configured to fit a pre-1959 MGA with low starter position. It may also be used to install a low starter gearbox in a later model MGA (originally high starter 1959-1962) along with an MGB 5-main bearing engine (1965-1980). As a commercially available part it is Moss Motors (USA) part number 461-045. In early 2024 this plate is advertised as a "clearance" item, so maybe when the last parts are sold there will be no more. Then we would have to go back to modifying MGA rear plates to suit this application.