I did a little searching for some info on ATF type of fluid to add to an automatic transmission (auto trans / auto tranny) but found some fairly old links. I also consulted a a buddy of mine about the subject and wanted to post my results.

In the FSM, the auto tranny required Dexron-II or Mercon-III. Since this is no longer produced, I sought out a suitable replacement. There are several options out there but settled on this: Valvoline Dex/Merc ATF. And the same fluid can be used in the Power Steering system.

As per the spec sheet on Valvoline's website:
Valvoline DEX/MERC ATF (Automatic Transmission Fluid) is formulated with premium base stocks and advanced additive technology to meet the challenging demands of an automatic transmission environment. Its responsive low temperature fluidity is beneficial in both electronic and hydraulic controlled transmissions and transaxles.

It is recommended for automatic transmissions for pre-2006 General Motors and post-1981 and pre-2007 Ford passenger cars (except where a Ford MERCONŽ V* or MERCONŽ SP type product is specified) and light duty truck transmissions, as well as many imports.

Valvoline DEX/MERC ATF may be used for service fill where Ford M2C138-CJ, M2C166-H, MERCONŽ, DEXRONŽ,** DEXRONŽ-II, DEXRONŽ-III, or Allison TES-389, is recommended.

This is what the product (quart bottle) looks like:

 

I replaced the old trans fluid today with the Valvoline Dex/Merc ATF today using a vacuum fluid extractor (ie: Schwaben 6.5 Liter Extractor system). It was a fast, simple, and fairly clean process. The old fluid was pretty dirty and darker-red/light brown in color. Additionally, I extracted close to 4qts of ATF fluid. The trans was considerably overfilled! After the trans pan was emptied, I added the new ATF via the dip stick. It took just about 3qts. Once filled, I vacated the power steering and topped it off with the same fluid.

I then started the car and let it warm up. I quickly shifted from Park to Low gear a few times then put it back into Park. Shut the car off then allowed the fluid to settle. Presto! The fluid was right at the FULL mark! I also verified that the trans would transition into each gear by slowly selecting each position on the shift leaver. No problems were noted. I also noted a smoother shift pattern during the road test.