I edited the thread title so members would have an idea what you are doing.
You will need to change the drive shaft Yoke to 32 spline of the 4L80E and length of drive shaft will be shorter. I would suggest mounting the trans and measure for length
Build or modify a crossmember for the mount
There are wire pigtail adapters available to convert from 4L60E to the 4L80E , you will need the PCM re-programed for shift sequence of the 4L80
Depending on your engine size, there should be a flywheel available to use with the new trans combo
Dont worry how old you are... it is the mileage on your body that adds up.