Left or ride side really isn’t important, other than the driver side is probably more convenient. The main issue being the clutch master cylinder needs to be mounted at the same height on the firewall as the centerline of the brake master cylinder in order to keep the pedal ratio/push rod stroke correct. Every kit I’ve seen with the clutch cylinder on the driver side of the brake booster mounts the clutch cylinder much lower than the brake cylinder. The only kit I’m aware of that addresses the pedal connection issue is shown on the following link. Post #44 shows one solution to retaining the correct pedal ratio/stroke.

http://www.67-72chevytrucks.com/vboard/showthread.php?t=362375&page=2

1960 GMC 1/2-Ton Pickup Truck
In the Gallery
Updates in the DITY Gallery
Now cruising in the Passing Lane