Thanks for your thoughts. Maybe I could have worded it a little better, but thats just it, I don't have "a matched set, be it 42RH, truck, 904, whatever. Just need a dipstick in the tube it left the factory with" hence my asking for a correct fill level in relation to something within the transmission itself.
The tube that came in the truck 42RH got smashed, kinked, rendered unusable, and being short on space, I tossed it since it wasn't going to fit in the finished project anyway. I located a 904 tube that fits in the car, but I only have the long dipstick that came with/fit the transmission in a truck application.
" Best bet is to just keep the tube and stick together as a set." might be (is) a true statement, unfortunately that ship left port a few years ago.
If (for instance) someone says full is right at the gasket level, then I can put it together then measure how far below the hole the gasket is then engrave my full mark. "full right at the top of the valve body" would be a little trickier, but since I have the transmission out still, I could manage that. Factory matched tube and stick is what I can't do.