I would guess, you would want a WC T-5 . WC= world class, you do not want to swap in a non WC trans as it would not be as strong. .You can tell if it is a WC t5 by the bearing plug/cap on the front face of the trans, at the 7 o'clock position of the input bearing retainer. on WC t-5's the cap will have timken written on the out edge, and non-WC t5's the cap will look like a engine coolant plug.
The input shaft bearing retainer, would normally be made from aluminum in stock form , so you want to change that out to a steel one
when you have the input bearing reatainer off, take a look at the bearings and race, if it looks torn up, it will take a lot of time or cost alot to replace the bearing , since you have to take apart the trans to pull the input shaft.
As far as the endplay in the input shaft, according to ford there should not be any endplay. but according to my SAE mech at ford, it is ok as long as it does not touch the sides of the retainer,
Since I changed to a steel retainer, I just corrected my bearing play with a shim kit from ford. this kit comes with about 50 or so shims. (thats why it costs $105. I was able to get almost no play, but still turn easily w/ no binding. note* a dial caliper helps. just keep test fitting shims in and test fit the retainer with all 4 bolts torqed down. Basically,You are just setting the preload on the bearing in the retainer.
also there are alot of good write ups on the web
oh and make sure you find the correct speedo gear BEFORE you put the trans back in ...lol
have fun
-Geoffrey