Try doing a search under "Albion Gearbox" on the Forum.Dave Dunphy,my hero, has done exhaustive posts on this, and many other topics. I believe the Enfield gearbox you need for internals is the late 1940's J8? model. I seem to remember that later models have different mainshafts at the very least. I'd go for the "TT Industries" gearbox as long as you've got deep pockets. Why risk blowing up a magnesium 'box that is probably only fit for a museum anyway. The other option is a Norton/A.M.C. "NA" series gearbox. Although not strictly "Period" they are available, robust, with the right layshaft bearing fitted, and spare parts can be had. Next question, do you plan to race the bike?
