At this point I don't see why you couldn't just put spacers between the disks and the clutch thrust bearing, then back off the nuts on the ends of the shaft to suit. I don't see why that would affect size of the correct shim stacks, since it allows both plates of each clutch to move outward. No doubt Gadge will sort me out if I'm full of prunes on this.
The nuts pull the inner races in the clutch pulley bearings hard against the drive shaft shoulders I think, grumpy. So it wouldn't just be a matter of backing the nuts off; shims between the shoulders and races would be needed. I'd say equal shim thickness on both sides would be necessary, too. Then the clutch discs would need to be shimmed, to suit the wider pulley spacing.
