Here's what I'd do,

Change the front & rear seals.
Adjust the bands.
Install a basic shift kit.
Let A&A advise on what governor to update to.
Get a deep pan and/or cooler.
New filter & fluid (Type-F).

If you can, inspect the old driveshaft of the New Yorker and see if the slipyoke is galled or smooth. No sense in marring the D-shaft of your Superbee if the tailshaft bushing in your trans is toast. Been there.

Adding more capacity of fluid is going to assure you a longer lifespan since heat is the number one nemesis of the transmission.

If you can change a governor, you can put in a shift kit.