Today I got my GSL-SE LSD differential, drive shaft, etc.

Now that it's off, besides cleaning and painting the outside of it, what should I get for it to freshen it up besides changing the fluid?

I'm so excited to finally get rid of those drum brakes!
Not to mention my new lug pattern! YAY!!

 

If your not going to be rebuilding the differential,be sure you DO NOT remove the center nut on the driveline flange.Its nearly impossible to get your pinion bearing preload back the way it was since you cant measure the load with the diff carrier and pinion oil seal in place.

I do recommend some new U-joints or even a custom,large driveline since your supercharged,which increases driveline killing torque quite a bit.Your call......

The rear axles should be pulled out so you can check the wheel bearings,they are a common failure point.That also gives you the opportunity to change the axle seals and inspect the splines for any twist(abuse)
Do a once over on the brakes,and dont forget to install a disc brake proportioning valve up front......

 

To piggy back, a new shaft with replaceable joints is only~$250. With all of the work you have in the car it's a good investment. And you'll love yourself for it when you're joints do wear out. Strenght I wouldn't really worry about... I had half of a OEM shaft behind my V8 swap with no issues and the guy I sold the swap to is running it at the track with no issues.