[Accelo]

"It's not always about your truck but how you use it."
Perfect as nothing will last long with a driver without common sense.

The 4L80E and the Tubro 400 share the same ratios in first, second and third.
You correctly identified the bigger jumps between first and second in the 4l60E.
As the first gear ratio, across the board, has continued to move down over time as the final drive ratios moved up.
Will get you load moving easier with the 4L60E but the 4l80E has better ratios after that.
The different over-drive ratios, between the two transmissions, will result in a 129 rpm difference at 60 mph using 3:73 gears.
.70 on the 4l60E and .75 on the 4L80E.

The 400 and it's derivative are less sensitive to oil change intervals. Mostly because the bushings diameters are so much larger in the 400 & 4L80E than the 4L60Es. Keep the oil clean in the 700 & 4L60E and they will last much longer.
Glad you made it home with the load. Heater on at 103 deg had to be an experience I will pass on. But much better than at the side of the road waiting for a wrecker.
Cheers