KilRuf: Most people are using a regular diff that is tightened all the way down....so, it's not quite locked. This works the good, but it tends to loosen up when the diff heats up (during a run). The other options are taking the TC3 steel or aluminum diff halves, drilling a hold through them, and putting a pin all the way through both halves AND the gear. This will essentially lock the diff. This setup will give you alot of steering out of a corner, but take away quite a bit going in.
TigeRyan: There are two ways to do this. One, you could just put the tower on and get a set of the new arms. This will allow you to lower the ride height below 5.5mm, and get the benefits of the front tower.....OR.....you could add one shim under each mounting location when you put the tower on (3 shims total). This will raise the tower a little and allow you to go below 5.5mm. This will ALSO raise the camber link attachment, so be aware of that.
I would suggest just getting the new arms. They're cheap and less hassle.