A mechanical linkage with a lever up thru the floor on the driver's left connected to the existing clutch pedal/linkage should not be too hard to figure. Another obstacle in the way getting in and out, but simple. They had them in Model T's for nearly 20 years. One safety concern would be both hands off the wheel briefly while you shift....I hope you get it worked out and let us know how you did it.

Professional Novice