One thing to remember about LS engines is that if you can use them more or less as they come from the donor, then you can get by reasonably cheap. However, if you have to start changing parts, especially buying aftermarket stuff, they get very expensive, very quick. You should have room in that engine bay for a truck engine which will be the cheapest by far. Car engines tend to come at a premium.

The 5.3 truck engines are common and reasonably priced. The larger 6.0 and 6.2 versions make a lot more low end torque, but a usually carry a much higher price.

you may run into some interference issues with the LS truck accessory setup. The alternator will probably work. The AC compressor is mounted very low on the passenger side. That might be an issue. The power steering pump is in about the same place as a SBC.

Truck oil pans are pretty deep and may be too low, but there are plenty of shallower options.

Be sure to get the engine/trans combo along with the ECU and harness for whatever it came out of.