Sounds like the issue was sorted and success! just want to add when removing or replacing gears or parts with an interference fit that Heat and cooling IS your friend!
Of course a large Hydraulic press is VERY effective!
When pressing or removing a pressed on gear, Warm the gear itself with a torch NOT TOO MUCH, but warm it and wrap the shaft with a towel soaked in COLD water, and it can change dimensions by several thou" and separate quite easily. Same in reverse, Heat in an oven the part you want to expand, and chill in the freezer what you want to minimize.
Gears and trans shafts especially are very fiddly so have seen a few items break or crack when being pressed or taken apart,
When manufactured they are (generally) made out of a high quality steel and inside is somewhat malleable and soft, but the exterior wear surfaces receive a heat treatment. The depth of which varies. BSA were also a metals company and in my view,, much of their materials WERE built to a price but tended to be pretty good stuff compared to Norton-AMC and others.
I have seen some videos (Cough cough) that show some rather agricultural practices with gearbox rebuilding (Wont name names) but I shudder every time I think of it when I see Bodgers heating up engine or gearbox cases with a torch willy-nilly and then WHACK! beat in bearings with a resounding THUD with implements of destruction.
Cast aluminum is a particular entity and not meant to be heated and distorted in such manner.
CAREFUL and slow application of heat (Suggest start at 150 deg F., then up to 200 deg F , then 300 deg F ALLOW to normalize in each stage) then remove, press in or remove bearings or bushes, THEN wrap with a towell or replace back in Oven and allow to cool over several hours SLOWLY.. Expecting a alloy casting to hold tolerances 70 years on and then beating the Bejeezus out of it is unrealistic
