Artgirl,
Just becouse, "this will work with that, but will not work with what"
I have always liked after market clutchs better than stock clutchs when building a project.
I can get a Mc Leod RXT complete flywheel and cluth set that is rated for 1000 hp ready to install on any LS engine for $1000.00
AND it will fit inside the Kennedy Clutch Housing.
BUT, the stock clutch fits in most budgets, and staying in the budget is the goal,, unless you get tax money.
So keeping everyones options open, we will find, build or buy a bellhousing that will fit the LS9, becouse the Stock LS9 clutch is very large.
As long as the new clutch housing will cover that big monster, all the other clutches will fit..
The only other issue is the clutch splines, and 1 1/8 X 26 clutch hub is found in almost every brand cluth made, and CHEVY uses it all the time.
After all of this being said, if you buying a stock cluth pick your Year, Make, and Model, and stick with it.
Be sure to right it down so you can go to NAPA and a replacement, years fron now.
DeLynn