HI I am working on L1 visa and recently I happened to receive SSN no for my wife after filing my taxreturn with itin number. Can someone suggest me if I can amend my return with my spouse ssn will I be eligible to get the econimic stimulus payment. Please suggest.My tax consultant said it could be possible?

Yes, you may get it.
Many, in your situation, have filed resident returns with proper SSN and have received the stimulus rebate.
You can wait for your 2008 tax return. If you do not receive full amount of $600 now, then you may get the balance amount when you file your 2008 return, and you become eligible for the tax rebate.
For information on stimulus tax rebate read: Your U.S. Tax Return: Are You Eligible for 2008 Stimulus Tax Rebate Payment?