I am going to buy a GBB II driver with a 10.5* loft and a regular flex. In the future I might want to buy a upgrade shaft and was interested in knowing what some good choices are.

I hit the ball about 210-220 with about 20 yards of roll. My club head speed is probably somewhere around the 80-90 mph range. I would like to put a shaft in the driver that would help to increase my "carry" distance.

Kevin,
You would be surprised by the wealth of information available on the websites of the individual shaft companies. Just go to the Google webpage and start plugging in the names of some of the well known shaft companies. Try typing in Fujikura golf shafts, and you will get to their website which lists their shafts and recommended swing speeds. The Vista Pro 60 model may be a good fit for you. Same thing for Graphite Design golf shafts, although their shafts play weak,as their R flex may be listed as 70-80 mph, and they are pricey. Grafalloy and True Temper are two subsidiaries of the same parent company, and will link you to a site called www.shaftfit.com which will recommend a shaft of their brand based on your swing speed and desired ball flight. One site I would definitely visit is www.USTgolfshaft.com. They sell UST and Harmon shafts, and have a "video professor", an animated little guy who asks you questions about what your swing is like and what you want in a shaft, and then makes recommendations. The Striper J is a very nice shaft. Aldila also lists recommended swing speeds, and has shafts specifically tailored to specific ball flights, namely the Aldila One model which can be purchased for High Launch or for Mid Launch characteristics.
Also, two of the main component companies, Golfsmith and Dynacraft, list recommended swing speeds along with their shafts, and tell you what the ball flight characteristics should be.
A shaft with a high flex point or a firmer tip will hit the ball lower. A shaft with a low flex point or a softer tip will hit the ball higher.
One important thing to note is that the Great Big Bertha II may have an inner hosel diameter of .350 instead of the more common diameter of .335, so you would have to get the right shaft, and not all shafts are available in .350, although adaptors are available.
Finally, go to www.callawaygolf.com. Then click on woods, then Great Big Bertha II, then Tech Specs, then shaft options. You will see several shaft options that the club could have been ordered with originally for an added fee, and should be suitable as a replacement.
Based on what you said you wanted and your swing speed, I personally would go for the Aldila One High Launch model. It has 3.6* of torque, and weighs 67 grams before trimming. Even if the GBB II requires a .350 tip shaft (and I'm not sure it does), any decent clubmaker can get an adaptor ferrule through his component supplier.
Hope this helps and that it isn't information overload.
Joe Golfer

You might want to look at the Royal Precision Saber shaft. It has a mid-low bend point to help you get the ball into the air for more carry distance, and low torque for accuracy off the tee. And the price is pretty good also, at $39.50 from Golfsmith. It comes in 65 or 75 gram version so you have a choice of weight. I have three Rifle Graphite 65 shafts in my woods and I'm quite happy with all of them. You might want to pick up a Golfsmith catalog and go thru all the shafts that are listed. You will find the weight, torque,bend point and recommended swing speeds for each shaft. As Joe mentioned above, the lower the bend point, the higher the launch angle you will get off the tee. You can check the specs for the shafts and look at the price, and narrow your choice down to a few you like that way. Then if you have a Golfsmith store near you, you should be able to demo a few drivers with different shafts in them and pick the one you hit the way you want to hit it. Good luck with your search and your GGB II.