Trans fluid. 727

Fresh 727. What does that mean ? Is it all original Mopar parts inside or have the seals, clutches etc. been changed to another brand ? If so you need to know from the builder of the trans what is the correct fluid. Not people without the specifics of what you have. There are all kinds of opinions on fluids based on all kinds of different parts used in the rebuilds as opposed to what the factory recommends on a factory built trans.
If it was a new manufactured Mopar 727 with no changes internally, They would recommend ATF +4 today. Fluids are constantly upgraded over the years as they discover new synthetics with different properties that affect things like slippage, shudder, wear etc...
Transmission fluid

(by Bill Watson)

Automatic transmission fluid is added, through a funnel, to the dipstick tube on the passenger side of the vehicle. Many car parts stores sell a funnel with an attached hose, which fits perfectly into the tube. [For emergencies you may want to carry a disposable funnel.]

The transmission should be at its normal temperature before checking, and the car should be on truly level ground. Apply the parking brake firmly with the engine at idle, then shift into each gear, momentarily ending in Neutral - not Park.

The fluid level should be at the full mark on the transmission dipstick, or slightly below it - definitely not above Full. If it is below the "add one pint" mark, add fluid and check the level again as per above to ensure the level is between "ADD" and "FULL".

For smoother shifting and less wear in winter, use Chrysler ATF+3 or ATF+4 (there are numerous "universal" fluids, and one which conforms to Dexron III and/or ATF+3/+4 should work).