It all depends on what you want to do with it.
You aren't going to make too much better, in terms of towing a lot more. You've got a small block and a 4L60e, after all.
Now, you can make it *better* at towing whatever you towing now.
Your basic stuff:
Good trans cooler
Load range E tires
Weight distributing hitch
good brake controller
Then maintenance items: shocks, brakes, sway bar bushings, tune up stuff, etc.
If you have a line on a semifloat 14 bolt that would otherwise bolt in, I suppose, but I think thats a slippery slope, and I'd just bite the bullet and sell it and get a 3/4 ton if you need it...