1986 C30 BBC clutch diameter and preferred slave cylinder brand

[dan76]

I'm collecting parts to replace the clutch in this truck. However the parts store lists two clutch diameters....12" and an 11.??". The owner prefers the 12" but not knowing what's in the truck now does not allow one to get the correct parts prior to disassembly.

The parts store I prefer (as nearly all others in the area) do not stock either size clutch set and will have to order it with two days to receive. As the truck is a DD, the owner prefers I have the truck for only a day ...at most two.

Is the flywheel the same for both clutch sizes? Can I go with the 12" without issue even if I find the original size is smaller?

What brand of slave cylinder have folks found satisfactory? Again the parts store lists several brands (varying in price by more than 50 dollars). The owner wants a reliable unit but not at a unrealistic price as I do also since I'm installing the unit.

Appreciate the assistance.