... most of which you can get from a junkyard. The greatest expense in replacing a busted trans is the trans itself. And the 80 will cost you about 15% more than the 60. Depending on how much work you can do yourself it can be a few hundred more to double the cost of a straight 60 replacement, all told.
Keep in mind it's all factory parts, mix and matched. It's not like you are cramming something completely foreign in there, like the old school 'drop a 350 SBC into an FJ40'. If you don' thave the mechanical ability it's gonna cost you a lot in mechanic labor costs.
+1 to this. I am anticipating my 4l60e going out in the next 50k miles and have extensively looked into it. It is not a "direct swap, but if you can do your own work, getting a low mileage 4L80e, and the parts, will be a little more $ than a rebuilt or low mileage 4l60e if you search around for cheap sources (junkyards, the 4l80e and associated parts are a plenty, this transmission was in millions and millions of vehicles.) After that, it is pretty straight forward if you can do your own work, it will just be the extra time to install it and figure out the computer wiring changes. It is not hard, and there are a ton of threads online of the swap done. It is fairly common, and you won't be "breaking new ground".
For the money and time investment, the 4l80e, will be something you can rely 100% on, and will last forever. It is a much, much stronger transmission, and if you are at stock power, you will probably never ever break it for the life of the engine or even the truck. Even paying someone to do the labor, is still worth it IMHO. Think about it, instead of $1000-1500 for a rebuilt 4l60e installed, that will always be the weak point of the truck (of which these trucks don't have many), for $2500, you will have a truly bullet proof option. A rebuilt 4l60e would be fine and they do last if you use common sense with the temperature and use, but if we are talking running these engines to 300k under hard abuse and the truck chassis to much more, wouldn't it be nice to have a transmission that would do the same?
And to to OP, yes, it will do great for you, just watch the temps, and don't abuse it. Between my friend and I, we both have similar weight race trailers (6000lb) and I am at 220k miles on 4l60E with all the towing, being lifted and on 33's. He's not lifted, but we both are going strong at this point (He did have one replaced under warranty at 80k miles). I truly believe that the stories of the 4l60e's going bad are most in trucks without coolers/ towing package, hotshots dragging their suburbans at every stoplight, and the fact that many of these trucks last to 250k+ miles with factory engines, and the transmission goes before the engine does.