Shift tower.

[1946]

Hi all, a question for transmission specialists. I had cause to remove the gear stick housing/shift tower due to sloppy movement in the stick, waving about like a flag in the wind. I have a couple of spare towers,(2). All seemed to be different, one had no attachment for the emergency hand brake, one had fittings just in front of the gear stick, and the last had a position to bolt the brake lever on the RHS. The first had a smaller spring and a felt washer inside a steel washer with a place on the reverse side for the spring to fit over. I noted all three had retaining washers for the spring same as the valve spring.
Question, why and when, did these changes happen.
Many thanks in advance.