You cannot compare different OS'es, nor flash a different OS into a truck with the "normal" flash. There are two flashes, FLASH CALIBRATION (aka normal), and FLASH CALIBRATION AND OPERATING SYSTEM (aka FULL FLASH). That will let you flash the "wrong" OS into the truck, but I would not do that unless you have experience and an extra ECM just in case. It could have undesireable effects up to even killing the ECM. Or may run wonderful.
The LLY's have 3 OS'es if I remember right. Last 4 digits:
1668 - Original 2004.5 calibration.
1600 - Early 2005, wasn't put on many trucks, and dealer will reflash to 8758.
8758 - Latest 2005 OS.
If the truck is 1600, then you can FULL FLASH to 8758 without problem. I know you can run 2005 truck with the 1668 OS, but have only swapped ECM's, never full flashed to switch.
Basically, if you have a tune that is the right truck, but wrong OS, you manually copy the tune:
Desired Tune - One you want to load, but is wrong OS.
Stock Tune - Stock Tune in the Desired Tune OS.
Original Tune - Stock tune that is already in the truck that you want to "upgrade".
Launch EFILive and load Desired Tune. File Load Alternate Tune-> Stock Tune. Now hit the COMPARE button. Write down the addresses of all the differences on a sheet of paper, example B0727, etc.
Close Alternate Tune to avoid confusion, but leave EFILive running with the Desired Tune loaded.
Open EFILive again, so it's running twice. Make sure "units" match. Both EFILive's should be either Inch or Metric. EDIT>Configure Display Units>Select All>Imperial.
Load the Original Tune in the second EFILive. Save it as NEWRACETUNE as to not overwrite the stock tune.
So now you have two EFILive windows open, one is DESIRED TUNE, one is NEWRACETUNE. Go to your list, and type in the first ADDRESS in the Navigator Window Box of Desired Tune, then do it to NEWRACETUNE. Highlight all the cells (CTRL-A) in DESIRED TUNE, then hit copy (CTRL-C). Go to the NEWRACETUNE, then CTRL-A and paste (CTRL-V). Scratch that off your list. Repeat for the rest.
When you are done, load ALTERNATE on the NEWRACETUNE, the original tune and hit COMPARE. This list should match your written list.
Done. Yes, it's a PITA, but it takes only about 1 hour max, and is the safest way to go.
Don't do this between LBZ and LMM's files or stick and auto, because the truck will not run right. For those you should just build the tune on a dyno or by datalogging and driving.
