after swapping in my new 3rds, my driverside rear axle leaks bad. Looks like the leak is coming from under the drum area. What exact seals do I need? (Inner axle seal, Outer seal, Bearing?)

Sounds like the seal that's pressed into the end of the axle housing.   It might have been damaged during the swap.  You have to be real carefull sliding the axle shaft's in or out, not letting the weight of them rest on the seal.  They are not very expensive.  Hope this helps.