I've had the 550 board in the Color Classic and it's working fine with it. I installed 512k of vram on the board and it has 8mb of ram so far, with Mac OS 7.6.1 installed.

I bought a new floppy drive for it, but it refuses to work. A 128mb module that I bought fit on the 550 board, but system wouldn't boot with it, computer would chime but screen would stay black.