I'm installing a 4:11 diff in my 98C5 anything special I need to know to acomplish this?

You might go ahead and install hardened output shafts while you're at it. You suddenly have 20% (4.11/3.42ths) more torque, the stock ones aren't known for being the most robust things in the world. They are available various places I think -- I know Ed Potter at Lingenfelter can get you some--I got mine from them.