Type F. But in reality any atf will work in an old slush box. However Iโd stay away from synthetic and newer fluids that are high in detergents.
But you donโt say whether itโs a rebuild, or drain n fill or flush or just adding because itโs low.
The answer could be different depending what youโre adding fluid for but type F will work for all.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5โ turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold