What fluid for a 4-speed trans?

Check the FSM for your year trans... the recommended lubricants are listed according to temperature.
For instance, in the '68 manual it states for the A833:
Warm climate: Multi-purpose gear oil SAE 140
Cold climate: Multi-purpose gear oil SAE 80 or 90
or
Auto Trans. Fluid "AQ ATF" Suffix "A" (Dexron)
Also states:
"Fill transmission with Multi-Purpose Gear Oil SAE 140. If shift effort becomes extremely high during cold weather, Multi-Purpose Gear Oil SAE 80 or 90 should be used. Automatic Transmission Fluid AQ-ATF Suffix "A" (Dexron) may also be used in extremely cold climates.
So, check your year FSM- but I don't think the OD will differ much in it's requirements.
I usually don't argue with the factory recommendations. But some people will.