You have JB6 brakes now.
Far as I'm concerned, you're done. My truck started with JN3, I upgraded TO JB6--which is what you have now.
There's nothing wrong with the 11.x rear drums, if they're in good shape. There's no reason to "upgrade" to discs except bragging rights. MOST cheap-junk disc conversions will be a DOWN-grade.
There's really nothing wrong with the front brakes, either--again, if they're working PROPERLY. They're not weak, they don't have a squishy brake pedal. You'd want to assure that the pistons aren't getting sticky, and the calipers "float" on the rubber mounts like they should. The rotors shouldn't be excessively scored.
Be sure your ABS unit is properly bled, which requires a scan tool. Again, IF it's working like it's supposed to, you'd never know it was there until you need it.
Now, if you want bragging rights, you can add multi-piston calipers, enormous aftermarket rotors, or swap brakes from a newer truck. But there's not a thing wrong with the brakes you have--they'll stop the truck just fine even with a trailer attached. They'll have fine pedal "feel"--IF everything works like it's supposed to. But lots and lots of trucks--especially 1500s with the shittty leading/trailing rear drums--do not have brakes that work like they're supposed to, and that's created a reputation for poor braking on GMT400-series trucks.
Keep in mind that your truck does have low-drag front calipers, you NEED the stock Quick Take-Up master cylinder that has the third, high-volume, low-pressure chamber.
Hydroboost? Yeah...I suppose. I don't think it's as big an advantage as has been stated. But then, I've only got experience with ONE vehicle having hydroboost, and the brake "feel" takes getting used-to.