4L60E to TH400 question

[FamilyTruckster]

I am swapping my 4wd 4L60E for a 2WD TH400.

I will wire the neutral safety switch appropriately to the new hurst floor shifter and I will be getting the Dakota Digital VSS parts. I will also be getting the proper flywheel and spacer.

The fab work for the crossmember is a piece of cake, and I will purchase a yoke and have a new driveshaft made.

All that I have a question about is the tuning. I am building another motor for the truck, and stuffing it full of 80mm turbo goodness. But first, I'm ditching the 4wd components and swapping the trans. I daily the truck so my question is this;

How will the computer react to the missing transmission information? I will need to continue to drive the truck on a daily basis for 3-4 months while I finish up the turbo motor and swap it in. If at all possible, I would like to avoid paying a tuner to tune the truck twice.

An 80E is out of the question, so don't ask.

[FamilyTruckster]

Forgot to mention, the truck is a 2003 Yukon currently sporting an LM7