You might end up with water pooling in you disconnect housing. AFAIK the national 471763 is supposed to be placed at the disconnect housing, not at the diff.
From reading a bunch of write-ups it seems like not all D30 are the same. Some have a place for a seal at the diff, others don't, and several part numbers are mentioned as working in specific axles.
Here is a list of some that might work:
Chicago Rawhide 11343 (Same as 11340 just a bit deeper sides)
Napa 11800
National 710068
National 471763
Spicer 42500
Superior Axle 470160