Not as far as I know, different weight classes and all. I think it'd be a pretty good fight, hard to say who'd win. GSP might take it by decision.
Liddell is quite a bit older than GSP so there's a chance GSP could just wear him down, but honestly I think Liddell is (or was) a better fighter. There's no way GSP could take him to the ground, and I don't think he could hold up to Liddell's KO power. Then again I don't think Liddell has faced anybody as well rounded as GSP is, and GSP's age and agility would definitely be tough on him at his age.
Now if we're talking about Liddell in his prime vs GSP in his prime, Liddell would take it for sure.

Talking about some more realistic fights... I think Silva would give GSP a good run for his money.