IS700Z Drive belt diagram

Remove tension on the moving idler arm to get the belt off and on.
Since I have not seen one these you may need to find a way to do this. sometimes the spring can be removed, other times there is a square hole in the idler arm for pull bar, yet other times you have to use a ratchet tie down to pull idler arm to remove the tension on the belt. Of course you will need to pull the PTO clutch to get the drive belt off and on the engine pulley. The anti rotation pin is a 5/16 screw (bolt) that must have the nut remove to get the clutch off. The PTO clutch retaining screw [bolt] must be installed using Loctite 271 and torqued to 65 ft-lbs per the IPL instructions. Doing this may require two people as one got the hold the engine's flywheel to prevent the crankshaft from rotating while torquing the PTO clutch retaining screw [bolt]. Can be done by one person but it is a challenge.
Every OEM has their way of putting the belts on so we got to be good at doing puzzles. I just got in a JD 652R with so little clearance you can't even remove the drive belt from the pulleys without removing the electric clutch in the first place, even through it has to come off the get the drive around the engine pulley. But the PTO is blocking the getting enough tension off the idler pulley to remove the belt.