2007 Silverado 1500 classic engine swap

Hello all I have a bit of a strange question I have a 2007 Chevy Silverado 1500 classic with the L59 5.3L LS engine that I bought a replacement engine for from a salvage yard but I think the salvage yard gave me a engine from a 2004 with a 6.0L motor. I bought the complete engine, wiring harness, and PCM but I only changed the engine it's but ended up putting the intake and alternator from my original 5.3L on it I did try using the PCM that came with the motor but it runs like crap and flashes reduced engine power on the dash and had around 26 DTC codes so went back to the PCM that was originally in my truck does anyone know if the intake and fuel rail from the 5.3L will be sufficient if it is indeed a 6.0L like the PCM that came with it says it is? It's currently running but to me it seems to idle to low and sometimes dies when you come to a stop it will start right back up I don't have A service engine light on but the PCM currently has 4 dtc codes stored.

Is your 2007 L59 is a flex fuel vehicle, correct? If so, you'll need to swap the injectors at a minimum. Flex fuel engines use a different injector part # from the non-flex engines. I'd swap the intake as well, just on general principle.

Thanks for the info but I got it sorted I checked the block casting numbers and it is indeed a 5.3L like my original L59 gen 3 ls I then cleaned the MAF sensor which fixed most everything except I was still getting a O2 sensor bank 1 sensor 1 fault so I tested the wires going to the O2 sensor from the PCM and all was good there so replaced the O2 sensor and now everything is right as rain except I'm concerned about inadequate oil pressure possibly...

my first thing I look at on older LS motors with low oil pressure is the O-ring on the pickup tube...they are Notorious for getting brittle and cracking over time due to all the heat cycles they endure....once it cracks then it is sucking air along with the oil and instant low pressure....I've probably done 100+ LS swaps (currently doing one on a 34 Deuce coupe) from just regular motor for motor swap to LS conversions...we ALWAYS pull the pan and replace the o-ring if the motor going in is a salvage pull motor and usually the pan needs a new gasket anyway.

I wish I would have known about the oring issue before getting the engine put in I would have definitely replaced it I already ordered a new pump and pickup tube.

well, honestly if the pickup tube was a separate purchase from the pump, I would return it (unless you just really want it) as I can't remember the last time a pickup tube was bad (unless it got damaged from a rod or something else coming apart inside the motor.