Type of Fluid???

Ok Guys.....I have a new 904 (stock as far as I know of) that was built and installed in this car before I bought it. The problem is, that the tranny is missing the dipstick. Now, I have another 904 dipstick, I was just wanting to make sure I put in the RIGHT FLUID in the tranny before initial engine startup (engine is new as well). I went to the auto parts store and they said it took ATF-3.....but I seem to remember my 727 from my 71 Super Bee taking Dextron II. Any ideas???

Bob