Technical Checking 1956 Olds Jetaway fluid level

I just got my transmission back after rebuild, and I'm worried about starting the car without knowing how much fluid is in the transmission.
There is a little drop of ATF at the drain plug, which tells me, that there is some fluid in there but since it's the double coupling type transmission, I'd think it would show up on the dipstick, if the couplings were not filled yet. Plus it hasn't cycled through the radiator either.
But it doesn't show up on the dipstick at all.
(My '65 th400 shows fluid on the dipstick, even when the car is not running)

I'm worried I might mess up the transmission just idling in case there is not enough fluid in there.
Is there any way I can check that? Or would I only damage the transmission trying to drive without proper fluid level?

Thanks, Martin

 

What does your service manual for your car say? I just recently installed the automatic trans in my 1956 Cadillac, and per the manual on my car, you are supposed to fill the trans with 8 quarts of atf, and then while running in N and the engine up to temp, add fluid until full (Usually another 4 quarts) since the trans is a 12 qt trans.

 

After we had the trans rebuilt in my brothers 56 it held 14qts of fluid. I guess it depends on if the rebuilder put any at all in the converter.

 

Thanks for the replies, guys!

Here is a screenshot from my manual:


Sounds like I need a total of 13.5 quarts, but still not sure how to tell how much is already in there.
Guess I'll just do like @CHS***ANS42 said, put in neutral and add as needed...

What fluid are you guys using?
I'm planning on using Pennzoil ATF:

 

that one may be different, but my experience (torqueflites, p-gs, etc) is to fill til the dipstick shows full, run it and shift the trans through the gears, then you'll probably need to add. recheck after the trans is hot--like after a good run on the highway.