I currently have my 4 speed out and I am looking at it. I too replaced all of the bushings both ends) with only minor improvement.
The real problem seems to be the shift tube ( part # 168 on tranny blowup ) It has a vulcanized rod sticking out that is attached to
a u shaped clevis. There is a protective safety drift pin that attached thes two parts There is a vulcanixed fitting between the two parts. the rubber on mine has sheared and allows the tube and the u shaped part to rotate. This rotation allows the shifter in the car to move excessively I think that is my problem and it sounds like yours also. The tube is not available !!!! . I am looking for someone to repalce the vulcanized joint. If not, I will use some black rubber calk and fix the drift pin with a solid bolt. If you need a pix of the part, contact me and I will send a diaagram
Not sure, but I think you can remove without taking tranny out I was taking mine out anyway for a disc repair and noticed the problem
I will post when mine is complete and working