A TransGo 4L60E - HD2 kit will firm up stuff. A vette 2nd gear servo also helps.
The TransGo kit will give you control over down shifting to 1st gear . I can run my 5.3 Silverado against the rev limiter then clik off another gear manually
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.