Even if the Statute of limitation bars refunds on your 2004 tax return but I would suggest you to file the tax return for 2004 and report this additional income as a result of amended K-1 and the tax credit. This will offset your tax liability but will carry forward the remaining credit to the following year.
Link to relevant sections for your reference-
Let me know if you have any question.
Please note: This advice is provided with the understanding that all the relevant facts have been provided by you. Any change in facts might affect the advice given and hence may not be relied on in such cases. Nothing contained in this reply was intended or written to be used, can be used by any taxpayer, or may be relied upon or used by any taxpayer for the purposes of avoiding penalties that may be imposed on the taxpayer under the Internal Revenue Code of 1986, as amended.