Cecato,
The WSA can be configured to send 80 and 443 traffic, in the WCCP settings area (5.2.0+). There are some things you will need to be aware of before doing this though:
1. If you are on 5.2.0-x, you will not be able to inspect HTTPS traffic. Only version 5.5.0+ has the ability to decrypt HTTPS traffic. Because of this, it is not recommended to redirect port 443 on WSA version 5.2.
2. You will most likely need to specify a service ID other then web-cache. On most Cisco devices, web-cache is reserved for port 80 traffic only and cannot be changed. Any other service ID will work as you want it to.