Going from 6.0 to 5.3

SBE Turbo lq4 - currently tuned on speed density (13* timing)

I want to have a 5.3 file so i can pretty much grab a junkyard engine, toss it inside the car, flash the file from 6.0 and 5.3 vise versa and make very little to no adjustments for it to run good.

I will swap everything over..... heads (has springs), cam, oil pump, etc

If i change the engine displacement in HP tuners, and given that the 6.0 is 13% larger than the 5.3, can i just pull 13% fuel and be in a ballpark or is that not how it works?

As for timing..... the compression ratio lq4 is 9.4:1 meanwhile the lm7 is 9.5:1..... so id assume that very little timing will have to come out. Could i back it off 2 degrees and work my way back up? Or am i completely wrong about this whole theory?

Thanks in advance

It's not going to be exactly that simple.

Change the cylinder volume and go back over the entire VE table with your wideband to get fueling correct everywhere. I can see timing adjustments needed in the low end and coming up into boost because of the smaller displacement.

I'm not sure why you'd want it to be a quick click click and done, it's far cheaper to spend 2-3 hours redoing some stuff than spending $1,000-2,000 on a new engine because it grenaded the block and took out other parts along with it.