Yeah, don't mess around with the 5.0L. Seems they were the worst, underpowered V8, carryover from the 80s when they sucked the power of the V8. 190 HP! As you said, nobody wants them, for good reason.
The 6.0LS/4L80e is probably the best combination out there at a very economical price. At least around here they are around $2200-2500. Seems expensive, but you get a ready to drop-in power train, complete with wiring harness and ECU. If you can figure out the wiring, you won't regret it. 300-325 HP/380 TQ. Not too bad for out of box performance. Mods can you you much higher, but I'm taking stock vs stock, so we'll use that.
When compared to a full rebuild cost of your engine, it makes that $2500 price very affordable, and you step up the the HD transmission. I've got a few 2500 series GMT 800 SUVs LQ4 6.0 (a 2wd and a 4x4) and I'm very pleased with that combination. Both have 4.10 gears. Plenty of power, smooth and very reliable. Really no complaints.
Next option is a 5.3LS. Somewhere around 315 HP/320 TQ. I've got another GMT 800 1500 that I swapped a 5.3 LM7/4L80e from the original 4.3/4L60e. I got to say, the 5.3/4L80e is another great option since you have a 1500. Mine has 3.42. In a lighter truck the 5.3 is just fine with 3.42/3.73. That engine I got for like $450 or so, complete with everything. HP/$ ratio, this probably the best bang for your buck.
Last truck I own is a GMT 400 K3500 with the 5.7/4L80e/4.10. 255 HP/330 TQ. It's plenty torque-y off the line, but just doesn't have the mid to high range power. It's fine, but my experience with the SBC is they can have issues with distributors, missfires, and those spider injectors, especially after the 200K mark...not a fan of that system, but some guys like it. My truck is not a daily, so the SBC is just fine. I only use it like once a month at most. I would pick the 6.0 over the 5.7 if I needed a reliable HD truck though.
At some point I considered swapping a 5.7 Vortec in my 1500. You can get rid of the spider injectors, but requires a "Marine" intake. When I looked, the very few of those intakes that I found were like $600-$800 alone. I said screw that. You can also do a distributor delete on the SBC, but it's a lot of work. Same for the 0411 upgrade. Just do an LS and automatically get all of that, for way cheaper and less headaches.
Note all trucks I mentioned have the 4L80e. It's a great transmission for heavy duty use.
Generally, the LS is just a more advanced engine, there was more engineering and research used on it than the earlier Generation I/II SBC. It has distributor-less ignition (individual coil packs), fuel rail that makes injector diagnosis easier, and the ECU is also much more advanced with ignition timing thanks to the 24 tooth (or 58 tooth of the Gen IV LS)reluctor wheel. This book I read said the LS1 from 1997 ECU had as much memory as a desktop PC of the era. LOL.
There's a reason why those engines get swapped in just about anything. They are compact, powerful, reliable, and very economical.