Well y'all, it appears that the clutch issues have now been solved. I took JB's advice and examined the pedal box again and I was able to determine that when the clutch pedal was depressed, the pedal assembly was rotating and twisting toward the driver instead of the cable being pulled. That was causing the both cable to not fully engage the clutch and also causing the pedal shafts to bind prevention the pedal from returning all the way even though the assembly was recently cleaned and lubed. The cause of the twisting issue was the inner pedal mount twisting and allowing the pedals to twist. Interestingly, the inner mount seems to have been designed to have something of large diameter (maybe the shaft, maybe a locating pin) passing through the frame and then also being secured by a small off-centre bolt passing through the frame side. On my assembly there wasn't anything protruding to pass through the lower, larger hole so the assembly was only held in by the smaller bolt. I fixed this issue by tapping the pedal shaft for a 9/16-12 bolt and passing that through the frame with some large washers to serve as the locating device. Now it all works great! I'm thinking of also adding a U-bolt passing over the pedal shafts and through the body to help secure it as well.
The next major project is going to installing and wiring the new radiator fan, but I've encountered a new problem...
The passenger door is now stuck shut and I can't manage to get it open! I was attempting to swap out the push-button with one that has a key for the lock but now the door is shut and I can't get the latch assembly to rotate!! I've tried briefly to get inside the door and twist the latch assembly from inside but I can't get it too rotate. Now I have to figure that out! Any advice for me on that front? Anyone else with an S1 encounter something similar with the stype of latch set-up?