It took me 12 years to restore my car.
During that time I had the 727 rebuilt.
I did not put any fluid in it and did not run it at all for 8 years.
During the initial engine break in the o-ring at the dipstick tube was puking fluid.
Simple fix..
The car has been on the road and driven lots since November 2017 and no issues and no leaks with the transmission.

I think if the trans is stored dry (no fluid) and off the floor is should be OK.
Hope this helps..