I had the same experience with a 56 engine in a 54 truck. The PO had wedged the radiator forward and it flopped and rattled. So I bought a short shaft pump conversion. Pricey, but I thought it would cure my clearance issues and let me bolt the radiator securely. It did, but it did nothing to center the fan higher on the radiator. There were also fan clearance issues with the harmonic balancer and I was restricted to using a small stock fan.
In the end, I purchased a water pump adaptor plate ($40.00) which mounts on the front of the 55-62 engine and uses the early style water pump (available at NAPA #58-126@$51.69). This centered the fan on the radiator, gave me the additional clearance so I can run a later model 15" flex-fan, and uses a pump that is available locally.
Installation of the adaptor plate does require drilling and tapping 2-3/8" holes in the block. I've got some pics in my album of the install. This is the second engine I've modified with the adaptor plate.
The installation instructions with the plate are clearcut, the procedure is foolproof, and if you want to solve all your cooling issues I feel it is the way to go. I hope this helps.
Dave
