You could consider the cam GM puts in the HT383E. It's available from the GMPP dealers and sources. It will give a little more power and torque and works with the stock computer and emissions. Though it works even better with a tune. Hypertech's tuner works well.
One caveat is that this is a roller cam so there will be some other modifications and parts necessary. Overall this is a nice cam for these trucks as it's emphasis is on low end power where these heavy vehicles need and use it most.
The other option of course it to just do the HT383E engine swap. If you do that though it's a lot more money.
Aside from the cam swap, I would also consider doing the MPFI fuel injection upgrade. Not only is it more reliable than the original CSFI system, but it will improve throttle response, fuel economy, and emissions.
Another option is to put in higher ration rocker arms. You can combine this with any of the options I've discussed or do them by themselves. They will basically add lift (and flow) to your existing cam without adding duration, which is where you get into other issues. This is another upgrade that usually requires other changes, like new valve springs and possibly spring seat modifications. S reputable aftermarket parts supplier or speed shop should be able to advise you on this.
I've done the HT383E swap myself and an extremely happy with it. See my signature.
