shackles...how tall is too tall?

I have heard that chevy ful size shackles will work on the back of ans xj, and i think they would, the deminsions are about right, and standard ones are about 6 inches long, about one inch of lift. my question is because i have seen chevys with loooong shackle, about 9 inches and very strong. that would be about two and a half inches of shackle lift. Too much? Another question, with this type of lift, it would angle the pinion up, so would it do away with the need for angle shims? just wondering

Me, I wouldn't run shackles that long, but that is more my personal preference than anything else.

Re: angle shims: it's really going to depend on your individual setup, where it ends up at. For instance, on my BOR HD 4" pack, I removed 4 degrees of shim when I went from a stock shackle to a 1" lift dogleg but couldn't remove the shim completely.