>Some manual trannys actually do use ATF, but I don't think they
started doing
> that until after about '93.

I've got a mid-80s Toyota that does. Dunno when this trend started.

Anyway, a bit of browsing around makes me think that, with a Ford in
that span of years, you have to get a service manual and possibly
figure out which of two possible transmissions your vehicle has.

Alternately, you can take out the filler plug and stick your finger in
there. (This is actually how you are supposed to check the level on
many such assemblies. It's usually supposed to be full to the bottom
of the filler aperture, cold.) If the stuff is substantially more
viscous than any motor oil you've ever dealt with, it's gear oil.
(After being in service for some time, gear oil is probably also
blackish and has a bit of a rotten egg smell.) If it's red, about the
viscosity of motor oil, and smells like regular automotive
petrochemicals without that overtone of evilness, it's tranny fluid.

Either way, you can choose mineral-based or synthetic replacements.

A diligent person would get one of those cheap drill-powered hydraulic
pumps and some rubber tubing and change the fluid in the
differential(s)
too. This is much more likely to be gear oil. If you have
positraction pumpkins, be sure to get that kind of fluid, not the
regular stuff.

Cheers,
--Joe