If you meant can you attach the blades directly to the alternator, the answer is no. The rear thrust bearing of a vehicle alternator is not designed to take the tremendous rearward thrust that would be generated by the blades.
The other problem is the rpm for the alternator to reach full output is generally higher than what your blade rpm will be, particularly at lower wind speeds.
You could build a "windmill" and then utilize a v-belt drive, chain drive or other gearing to eliminate both problems. If I were to attempt it, I would take a look for a cheap source for a truck alternator or some diesel powered equipment alternator. These tend to be higher amperage output and are available in voltages higher than 12 vdc.
The other two items for consideration are parasitic load and maintenence.
Vehicle alternators utilize a small amount of electicity to energize the field. So, you are consuming some of what you generate, to generate more. So with x amount of wind and two identically sized alternators, the permanent magnet alternator will put more juice in storage.
If we assume that an alternator will last 100,000 miles without need of repair and that your average vehicle speed is 40mph, your usefull life of an alternator would be about 2500 hours. If you assume it turns 24 hours a day, the life would be just over 100 days. If you change the assumption to it only turns about 1 third of the time, it would still only last about 1 year before needing repair/replacement. How often do you want to climb (or lower) the tower ?
These two factors are the reasons that most people will recommend not using vehicle alternators in wind power applications.