Brian,
Having done this swap with my 261 in my '50 I would recommend going with the adaptor plate and a 216 water pump. I shortened the stock pump myself and found a junkyard pulley that fits right. While it fits behind the radiator, I can't run a mechanical fan, it just doesn't fit- it hits the bottom radiator hose. I am running an electric fan mounted on the front of the radiator. It works but I don't like the sound it makes.
A 216 pump would mount higher and solve all those problems.
