meanwhile, the 05 ECM I have has like 6 strange codes in it that I can't clear, so no go there. The only other pre-06 ECM I have is an 03, so no bueno there.
I have one here that has a 7/20/2004 date code and bears part number 3971608.
I believe it to be either an extremely early '05, or possibly and extremely late '04 model.