The 5 speed's are different in the SHO, I've seen people put the SHO engine in Ford Rangers, and they had to use an Aerostar bellhousing, with a T5 manual transmission, as well as some other modifications.
The SHO engine is a marvel, I used to own a 1991 SHO. I think the Thunderbird is a little too heavy for that engine though. IT makes the same torque as the n/a 3.8L, but has considerably more hp. If someone could lighten up the Thunderbird, THEN throw a SHO motor in, I think it would be a blast. My SHO had a LPM (chip basically), and underdrive pullies, and I could wrap that thing out to 8k rpm if I wanted.
Don't feel bad Max, that just means you have to hop it up some more, hehe..