That reed block will be fine. Install the new reed material on the old block...(I actually dremeled away some material on my reed block to open it up a bit for better/more flow)
As for the carb setup, I run the same thing.
I've got a 95 main in mine. 90 is really close to what you'll need. I've heard others have settled on a 93 main for their kits.
Remember to use the flat topper piece to the carb! The regular carb topper and elbow will not work!