I always install NEW oem Check ball Vents fittings on both transfer case TOP cover in view here , and thew J-30 trans too , they RUST in the closed position some times or indeed the wide open posiution some time or spring inside simply breaks or rusts away after 50+ years
this WILL allow moisture and water from rain on road to migrate in over the short term
low cost insurance after you install FULL SYNTHETIC Gear oil For sure 100% SOLID
i bet @65swb45 / Mark has some nice ones for you ..........