OK, aside from the aforementioned weaknesses in the V-belt's power capability, to the best of my knowledge, the pulleys should be interchangeable. You need to make sure that the alternators are both from the same side of the engine. On the older designs, you could rotate the casing on the alternator to accomodate left or right hand mounting, but a lot of the later ones are a single casting.
The thing to check is that the shafts are both the same diameter, and a similar length. There are a few small variations in shaft size.
The biggest problem you might encounter will be if the V-pulley doesn't fall properly in line with the existing set up as that will cause the belt to run askew and give all sorts of issues.
