The 4L80E is basicly a 400 trans with overdrive and lockup torque converter. It is strong enough to run in a motorhome. Its the trans you get with the 8.1 in the 3/4 ton Chevies if you don't get an Allison. The 700R4 or 4L60E will not last very long. They are light duty car transmissions.
You would either have to have an aftermarket controller (expensive) or a controler out of a diesel truck to make the 4L80E work. (The "E" means it is electronic and won't work without a controller.) It is probably longer than the 400, so the driveshaft would have to be shortened, and if the parking brake is on the back of the trans like the 310 that I had, you would have to deal with that.
There is also a device available that will let a 4L80E shift the od in and out in 1st and 2nd as well as 3rd, giving a 6 speed. Much like a Gear Vendors, but with lockup.