Standard capacity for a 727 with a stock pan is about 5 quarts.
If you are gonna change the filter and fluid go ahead and drain the convertor if it has a drain plug. It is behind the flat shield, behind the oil pan, on the transmission housing face. You may have to rotate the engine to find the small drain plug. Not all torque convertors have them today but the factory did back in 1970.

Draining the torque convertor will add between 2 and 4 quarts to the 5 above depending on the size.

I can't find a good picture but the dipstick should extend into the transmission about 3/4 of inch or so. Here is a small block tube for reference. The level for a 727 will be the same for all engine types.

The difference in a Hemi Dipstick should be the shape of the tube not the depth of the fluid.

John Kunkel is the resident Auto Transmission expert and may have better advice/pics.