You'd probably get more responses in the general forum, but to answer your question, the factory service manual calls for ATF. In my '75F model, I used ATF+4 since I drive mopar products and that is what I had on the shelf. I know others have experimented with different fork oils, if you search the site, you'll find plenty of different answers.
Probably the most important thing is getting the oil level correct. Too little and it will be bouncy, too much and it may be too stiff.
