I hope to provide a definitive answer to another power hungry 17 year old such as myself who may have a 2005 Silverado Z71 with OS# 12606961, who wishes to install a 4l80e hydra magic (coincidental autocorrect?) into his truck.
I searched many forums to find the answer to which I found only a partial answer, and the only 80e segmented 12606961 was for HP Tuners.. I have efi live. So my definitive solution was to probably screw something up and configure an earlier version of my OS to run my truck- I used 12592618, an older OS that was replaced by the new one for some 02 sensor emissions mumbo-jumbo.

TLR, EFI live 12606961 OS 4l80e swap users can swap in a 12592618 OS with a 4l80e segment and everything will work fine. Don't forget to change over your VIN

 

Thanks very much for putting this info out. I've spent most of today searching the web on this. I just finished my 80e swap and fired up EFI live for the first time to find out I have some PITA OS number... Its been about a year now, how is your truck working? Did you have to do anything else?
Thanks

 

Now to reflect back on this, everything worked great, copy over all the info from your stock tune into the new OS and make sure all the values are the same, your fans are set up correctly and whatnot. This truck has been running awesome for almost a year now and has never had a hiccup behind a blown 6L yet. Sorry I didn't see the reply, you can PM me and I'll do my best to help you.