A little creative torch work, or possibly even some welding should put the shift knob in a different position, but it sounds like you need something on the order of the shifter we used to fabricate for controlling a Brownie on a big rig. A small ball joint or tie rod end bracketed to the floor provides a multi-directional pivot, then drill and tap a shift stick to screw onto the thread, and you can use a clevis at the right height above the pivot to control the length of stroke. Difficult, but not impossible to fabricate, and big-rig truck mechanics have done it for decades.
Jerry
