RE: What motor is in the LS?
Sleeper, you're right.
The LS is available with a 3.0 V6 or the 3.9 V8. These are what Ford loves to call "Corporate Alliance" packages.
LS, X-Type, and S-type share the 3.0 V6 as is.
LS has the optional 3.9. In S-Types(Optional),XJ, and XK, it's modified to displace 4.2L and is available with a supercharger.
Both engines are phsyically smaller than our 4.6s. Just by looking under the hoods, I don't believe a 4.6 would even fit between an LS's inner fenders! The 5R55E trans is much smaller and narrower. The bellhousing pattern is very different.
Now, having said all that, I'm sure every Ford Fan out there has seen pictures of the "SHOgun", a Festiva with a Taurus SHO drive line. If someone wants to bad enough, anything can be shoehorned and jerry-rigged into anything!