the 4 cyl and 8 cyl t-5 are different. the 5.0L mustang t-5 gearboxes have cast-in identification numbers on the left side of the main case, just forward of the rear face, on the extension housing's shifter tower. 5.0 t-5 shifter tower numbers start w/ "13-52-065." the diff. is "world class" vs. "non world class". i could fill up the rest of the page w/ other minute diffs. but thats the main jist of it. i would recommend buying "The Official Ford Mustang 5.0: technical reference and performance handbook, assuming u don't already have it. its like my bible now. as soon as i can i'll post a pic of me sleeping w/it under my pillow.
There's an age old debate about which to use, and a lot of people think that just because the 4 banger trany was for the 4 cylinder car that it's going to explode if you put it behind a 5.0...well, they ARE weaker, but for a mostly stock 302, as long as you don't miss any shifts you'll be fine. I've got a friend who swears by them, he won't run anything but them. They're actually a cheap way to lower your gear ratio as opposed to getting gears. He runs low 13s in his.