The picture of the gasket is my proposed solution. Its a very high quality gasket that should solve the issue once and for all. I would have definitely used it first if I had known about them. Currently between the axle and differential cover is black RTV - pretty standard.

I'm working a temporary fix until I get about 300 more miles on the new gears behind the diff cover. Then I'll pull the cover, scrape off all the RTV and go with the lubelocker.