belt squealing/ water pump to alternator alignment.

[j.rigby15r]

So I have a 64 with a sbc 350 that the belt is squealing really bad when I first start it up or when it's cold and rainy. The belt I'm sure is old and I know it is adjusted properly. I have a stock pulley on the alternator and a chrome one on the crank and water pump. See images below, but I think the noise is coming from the water pump and the alternator. It looks to me if the alternator sits a but in from the rest. If this is the case can I shim the alternator out a touch to align everything up? Or is there something else I should do? It doesn't scream all the time just enough to drive you nuts. Any help would be appreciated. Oh and the belt never seems wet when it's raining.