The change for 1997 was for lube to the rear planetary gearset. You will notice that the return cooler line fitting is towards the back of the case (not unlike a torqueflite) rather than next to the to-cooler fitting behind the bellhousing, like the earlier 4L80E and most other RWD GM transmissions. There are a bunch of internal changes, but the only external one is that cooler line fitting, which routes cool lube oil directly to the rear planetary set.

I wanted to recommend Lentech, but couldn't remember the name.

You can go without overdrive if you use a taller rear gear (like a 2.76) and a lower first gear (like 3+) to get you rolling. That's what you can do with a Lenco. The main advantage to having a lower first gear, direct drive for your top gear, and taller rear gear, is to keep driveshaft speeds down, and gear lube temps in the rear down. However, it's a moot point since you already have your rear done.

440shorty