I did that to my last car (92 Toyota Paseo). It had a big clunky rubber shift knob with a button on the side and an O/D button. I relocated to the O/D button to a rocket switch underneath the e-brake and bought a shift boot to put over the shifter.
The problem was that the shift stick was an oval and the shift knob I bought had a circle opening. It was one of those knobs where you just press the whole thing down to switch gears. So I had to take a hacksaw and cut the oval in half about 1/2" down. Then I installed the knob and it was done.
