Do you have an external trans cooler as well as the radiator trans built in cooler?
in your case disconnect the ATF line at the radiator (yes ATF will dribble, you can park with the nose up...) then connect both line together.... either with a union or using a single hose if you have slip on barb connectors which is probably the case as someone must have replaced the radiator at some point in the last 40 years.
These connections need to be tight, as soon as you are starting the engine the trans fluid will circulate. No need to start the engine first, check if coolant is leaking in a first test... then warm up the engine and monitor for leaks.
BUT if you have the OEM set up which are crimp on hoses and on the other side i a flare nut fitting -forgot the name- on the solid metal transmission line ....this is trickier, let's what you have?
my set up with external cooler