Believe DexIII/Mercon. TREMEC recommended to me not to go for the Mobil synthetic version.

When shifting mine, its worse doing a granny shift (50%). For spriited shifting I just push faster and a little harder (not forcing) and the syncros engage w/o complaint (they don't have time to think about it). I suspect movement of the engine trans affects the crispness of a granny shift. Some members indicated ditching the hydo mounts for the engine improved shifting. As long as the shifter is on that whimpy shifter brace that moves around, performance will be compromised ... but it's quite and does not rattle, something apparently coveted by the Ford marketing group.

Top loaders forever!!!