6.0 liter to 8.1 liter swap

[Demented]

Hey Guys,
Im new to the forum so please bare with me for being a newbie. lol. I did some searching and either didnt see or just didnt find the answer I was looking for.

Here's what Im doing.
I have a 2006 chevy 2500hd pickup with a 6.0 liter and a 4l80e transmission in it. This motor is all stock except for it was once tuned by a friend with HP tuners program many many years ago. ( it was NOT locked). I am in the process of switching motors in this vehicle. The new motor is a model year 2005 8.1 liter that came from a donor 2500hd but it had an allison transmission behind the motor. I have the entire engine including wiring harness and computer.
From all the research I have done it seems like the current 2006 6.0 liter wiring harness and sensors are identical to the donor 2005 8.1 liter.
So my intentions are to swap the 6.0l with the 8.1 liter using the current 4L80E transmission and 6.0 liter wiring harness and computer.
So where im running into an issue is this. First I want to save the 6.0 liter program for a "just in case" situation for a different vehicle at a later date. I might use this motor in a different car. Second I want to download the donor 8.1 Liter stock PCM program from its OEM computer to use the file in the 2006 6.0 liter computer. How can I do this? I am under the assumption that In order to download and save two different programs I would need to buy a second vin licence. Also only thing I dont have from the donor 8.1 liter is the actual vin number. Will this be an issue? If I can switch over file my intention is to adjust the tuneup on the stock 8.1liter format to fit my driving style.
Can someone give me some insite and pointers on it? I have the V2 Flash scan.

[ScarabEpic22]

You can read and datalog unlimited controllers for free. Only when you flash a controller for the first time are you required to license it. Just hook up your FS V2, read the stock 6L PCM out. Repeat for the 8.1L PCM as well.

Once you have the new 8.1 installed, you can either use the existing PCM (factory for your vehicle) or the 8.1L PCM. I would suggest you use the factory one and change all of the spark/VE tables to match the 8.1 or use the 8.1 PCM and find an 06 OS to flash into it. The engine doesnt care 05 vs 06 OS as long as the calibration is correct, but the vehicle might.

If you want to run the 8.1 PCM (they're the exact same PCM btw, LS1B 1MB, just different OS and calibrations), you will need to either segment swap or find another 8.1L OS that has a 4L80E behind it as the Allison has it's own TCM. 4LxxE dont on the LS1B, the PCM controls both the engine and trans.

Start with reading the PCMs and posting the files up here, might be able to help more with them in front of me. Also, the VIN for the 8.1 will be in the PCM once you read it out. :)