the ="Ford" fluid will make the shift firmer!! use that!! The GM fluid will protect it longer !!=slicker than ford stuff! Yet use what ever is formulated for fords-my best thoughts! Royal purple works good also! Just depends on weather new / rebuilt or just a used tranny!! I also will say this= if you are not to opposed to some solid shifts-not baby smoothe ones- id suggest installing a transgo shift improver kit -done for towing or one from B & M automotive!! I did this long ago to a th350 tranny with 156,000.miles & after 30+ years -& countless miles on it now!!=that still will chirp the tires in 2ng gear shifts!! Never any problems since that shift kit !!