Whatever you decide on remember if down the road if you decide to add a shift kit most after market stuff my well not work unless you have a rebuild that's close to stock.
What are your plans for it? In most apps a ford A servo will do but they make bigger, get aode internals (all stamped steel instead of cast) and a wide ratio gearset is nice if you can find one for a decent price. If your aiming just for the strip and barely any street driving (if your making bigger HP numbers) I'd just upgrade it to a 1 piece input shaft and do away w/ OD but if its something you want to cruise on the highway be sure you at least get a hardened input shaft (this is one of aod's weakest links for the most part). I used a transgo reprog kit and am for the most part happy with how it shifts but beware of these kits, or any other kit that says "Allows for WOT shifts into 4th!" .... you REALLY don't want this Lol I wish I would have known what I was doing a little more when I rebuilt the thing but at least it goes and shifts well .
The guys over at http://www.clickclickracing.com/ have a TON of useful info if you want another place to browse through.