Not sure where $800-1,000 5.3's are, but my local yard has 3 low mile DBC 5.3's for $450 a pop with their guarantee, and there is a local guy who parts out the trucks and will sell you an engine he can fire up for you for $500 and include an un cut harness. High mile engines are better for boost but are also cheaper. If your paying $800-1,000 and not getting a 6.0L your cheating yourself. You could add in Holley Terminator X and be in for around $2000. People do it every day.. Also running a 4L60E isn't really a good idea. Once you wake a 5.3L up and remove the torque management from the system and any little bit of power adder, a 4L60E is on life support. Adding senders for the original gauges is trivial. L31 is a great engine, but your going to find pooched out high mile junkers these days. They don't age like the LS engines and there are now less of them to go around. They only existed from 1996-2003. Keep your costs relative and you can get more out of an LS. Walking in a U pull it, any 2003+ Tahoe or Suburban has a 5.3L.
2014+ LT engines are where even more power sits, but a basic LT 5.3L will set you back $3k
But OP does not want an LS.
It seems the junkyard pull outs of the ls, pricing depends on location.
ALSO, Some yards "guarantee" isn't worth the ink to type it . To a shop a "guarantee" that is nothing more than if it has issues well, give you another, but you foot the labor time to do it twice, is worthless.
Like I stated in the other post, I'm sure there are 5.3 ls out there for 500 bones. Depends on what and if you value your time and the roll of the dice that it is a good unit.
We have finished a few of these swaps that the vehicle owner started .
If I was the thread author and was to entertain doing the ls swap. I'd do my own research on what it has cost others that have dropped one in their square body truck, and the honest cost of all the things requires beyond the take out unit.
Including the making the truck ls a/c compressor location work in the 73-87 gm trucks.
To the DIY guy that can risk the engine not being what the yard or person said it is. I am not here to tell them not to go for it. I stated in my other post that ,shops and folks getting paid to replace engines can not afford to do it twice. Job time promised,labor cost, comebacks are reasons we get parts/units from one yard and not a few of the others.
The thread author said he is on a budget. What that is, is for him to know, And why I would advise he do the research on what it takes from others that have done the swap in his type truck.
The true beauty of the ls engine is the number of good strong running gen 1 350 Chevy small blocks out there for sale complete for 150-200 bucks, that were pulled out because the person wanted the ls engine.
They maybe out dated and old tech. but If all you need is a strong solid engine. That is stone age simple, you can not beat it.
Most of the truck Vortec 350's trucks are in yards because of the pop it valve spider central efi, the long block is just fine, or the 4l60e(7004r) gave up the ghost.
Another issue with the take out ls that everyone glosses over is the o.e.m. ecu is looking for a bunch of sensor input data and module input data, That are not installed on/in the vehicle you swapped the ls into, setting off the SEL light (check engine light) . So now you need a buddy with a tuner that knows how to delete the inputs you did not install that the donor vehicle had.
It is not as simple and easy as may make it out to be, at least if you install one correctly and don't have the ecu pulling power because the SEL light is on, or would be if you installed it.
Many folks are making silly power on junkyard 4.8 ls and a ebay turbo.
like most things in this hobby, it depends on skill and budget.
I wish the thread author best of luck with whatever route he picks. best way to not not have surprises in the middle of an engine family swap is to pick the brains of those that have done it to the same vehicle.