Ugh. Yeah, on a 9" wheel you need +36, If I remember correctly. Whatever I have for offset is what you need, they're brads wheels, (baggedtaco here on the board) overall diameter doesn't matter for inside outside fitment of course, but I know I couldn't fit a 9" wheel on my car with as low as I am (and I'm not as low as you) if I didn't have this exact offset. Send brad a pm, he's friendly and helpful and would definately know better than anybody.
If you get a 9" wheel to tuck enough to lay out, please post an informative thread or remember to pm me if you would. In the future I'm looking to lay out on a 9" and need to know if it's worth the trouble (and what needs to be done) depending on what overall tire diameter you figure out will for sure work. Even if you do it with 20's the information will still be helpful to me. I'd really appreciate it.