The LQ4/LQ9 swap with a good cam and long tubes would be my choice. From there all you really need is a converter and some traciton aids and you'll be in the 100mph trap speed range or better. From there you're an easy nitrous kit away from 110mph traps.

To me gears are not worth the money you could be spending on other proven HP mods.

 

The STS kit will work just as well on a 4.8L as it does on any other motor. Thre is nothing wrong with the 4.8L.

 

another vote for a 6.0 swap, stall, long tubes, traction stuff and some tuning. easy 13's and with it dialed it perfect and on a good day maybe a high 12.

 

everything you can do to that 4.8 you can do to a 6.0 and have much more horsepower.