I thought they have a side fill plug?
It's been a long time so I am not sure.
As long as you do not try to speed shift those trannys & down shift hard into 2nd gear it should be OK for a while, just do not try to be too rough with it.
Also, if you start off in first gear let the engine turn some high RPMs in 1st & then let off the throttle & let the engine do the braking, those transmissions do not like that either.
MBHD