Few things. First, I just walked out to the car and can confirm that you'll need a T50 bit to remove the idler bolt. Second, that bolt is NOT
reverse threaded on my '97 Bonneville motor. I did a little research and came up with this;
Originally posted by- Echo SSEI
"Unless they changed something in 2000+, the Series II bolt on the tensioner pully for the supercharger is reverse threaded. Conterclockwise to tighten the bolt (and release tension) but clockwise to remove the bolt."
They're talking about the pulley you've highlighted in blue, not red. I don't see why GM would have changed to a reverse threaded bolt for years post '97. Just remember that it will be very easy to strip the aluminum post that the tensioner mounts to, so you'll have to hunt down a replacement post if you force the bolt the wrong way.
The part you've referenced from O'Reilly is the pulley for the blue highlighted tensioner. You want the larger metal pulley with the rolled front edge
; Goodyear part number 49006, Dayco part number 89007.
Tips on installing the belt. Don't let this intimidate you, it only looks complicated. After two or three installs you'll be able to do it in your sleep.
Make sure you get the belt lined up correctly on the large crank pulley, its easy for the belt to track a rib off while you're playing with the tensioner; which in my case has caused the belt to squeal a little. Route the belt over every pulley but the automatic tensioner and pull the belt tight with one hand, slack the tensioner with the other and slip the belt over it. Let off the tensioner and you're golden, but go back and be sure the belt is aligned on every pulley, particularly the two ribbed pulleys.
One last small detail. The car will be completely fine operating without the supercharger belt. There are no mechanical dangers of doing so, and the PCM will adjust the fuel trims accordingly. The negative intake pressure will spin the supercharger blades as it pulls air past them, so don't be alarmed if the supercharger pulley is spinning without belt. The car will be an absolute dog for power due to the 8.5:1 compression ratio. Once again, all of this is completely fine and won't harm the engine in any way, I've driven mine in such fashion many times before.
Good luck bro. Be sure to post about how the install went, and of course feel free to ask more questions.