retired 15

good Morning, I am alittle confused on a project that i am doing. I have a 2000 gt convertable . I bought the vehicle with a seized 4.6 and a automatic trans. I am in the middle of putting a 2004 4.6 out of a low mileadge lincoln and the trans is out of a 03 stang. The problem that the shop that is doing the install is that they are telling me that the flywheel is not the right one and will not bolt up to the converter. Any help would be great thank you.