So here are some options for you.
If you are on a budget and want some more power and reliability, a good old small block is the budget friendly choice. If you are savvy you can search fro all the parts you need, build the engine even break it in and runit before ever opening ghe hood of your car. You can make great power, good economy and the thing will live almost forever. They really are hard to screw up. Find someone close to you who can help. If you are near me I am more than willing to help.
If you have bigger budget and want some more cool / reliability / eceonomy then you can go for the 5.3 to 6.0 LS swap. These make great power excellent reliability and once complet are just like having a new fuel injected car. It will take a little more time, a good tuner to help you out but the cost will a little more with some extra time to do the swap.
Plenty of info out there on both these options, just choose what you can afford.
Hope this helps.