Speedo a no go.

Sounds like the only real way to fix it would be to replace the cable and housing. I had kept the original housing and just replaced the actual cable to make it easier (and also because the new housing didn't have the clip) but I guess to be sure I should just replace the entire thing.
The sheathe makes a long slow 90 degree turn under the drivers seat. The cable would wear the sheathe right there and cause problems. The entire thing isn't nearly as expensive for your model compared to others like early A. Price check the 64, 65.