Dexron 3 would be similar to the factory fill. They have friction modifiers in the fluid to “soften” the shifts. They type “F” ford fluid does not and hence makes a good choice for us that prefer a firm shift without buying the crazy expensive aftermarket “race” fluids back in the day.
So, if your servicing an existing system, dexron, if your building and filling from new, type “F”
Cliff Ramsdell