I belive you will have to fill in one of the coolant ports on the cleveland heads as they dont line up with the windsor block,attention will also have to be paid to the head gasket,make sure the block is running flat pistons or there might be clearence problems withe the valves.
I've always wanted to do it. Even when I had a 351C-4V. I actually wanted to build a 408 stroker Clevor. Those heads really need cubes. It's hard to beat the kool look of Clevage heads!