There is a single on Classic Truck Parts site for 60-63 and 63-66. Wilwood has a universal MC for less, albeit smaller bore.
If you do your own, you will need to be familiar with stroke, bore, volume, area, pivot points and pedal stop. If you buy a kit, most of that is covered and the stroke is stated. The push rods on the MC and slave are adjustable somewhat. Not a big deal just FYI.
Thinking outside the bottle, I say you can use a 64-66 pedal assy. Even though it is not hydraulic clutch, just use the brake half as the clutch and modify it's rod for a single 60-66 MC. Remove the clutch pedal and modify the mounting bracket to fit up and under. Since the brake rod is made for a MC, maybe no mod to it at all. It will never know it's on a clutch.
Ebay example Just to get the thoughts going to think of options.
