Slight knocking noise after motor swap?

Hello, I recently helped my dad do a motor swap on his 88 k2500. The motor taken out was an 88 tbi 350 and it was replaced with a 95 tbi 350. I haven't actually heard the motor in person but he says it has a slight knocking noise when coasting or revving up the engine with no load. If the motor is under load it is smooth and makes no noises. I didnt have much time to look at the ecm data while running but I did notice it was running in open loop. What could be the issue with it knocking. The motor has 180k on it but was driven in another truck for a year before it was pulled and the other truck supposedly ran fine. Will the knock sensor differentiate between detonation and rod knock. If the knock sensor can hear rod knock wouldnt it pull timing and the motor would feel like a dog? The motor seems to have good power all the time.

Does it have a working oil pressure gauge? If so, what is the oil pressure? Is the noise present when the engine is cold?

The oil pressure gauge in the truck reads 60lbs but it seems to always read 60lbs. An analog oil pressure gauge is being installed.

My dads 71 vette (350) was knocking last year. It never made any noise when it was cold. After warm up and no load, you could really hear it when you goosed the throttle. The oil pressure gauge didn't work. Before blaming engine bearings I checked a bunch of stuff that can sound like a knock. Loose harmonic balancer, loose flywheel, exhaust leaks, broken rocker, loose rocker arm, collapsed lifter and anything suspicious that could be rattling. A stethoscope helped a lot. After all the listed checks were completed, I checked for a rod knock. I started the engine and began to remove spark plug wires from the distributor cap. If the knock goes away after you stop ignition on a cylinder, its a pretty good indication that the rod bearing on that connecting rod it bad. All 8 checked out on my dads engine. I hooked up an after market oil pressure gauge and noticed it had 0 oil pressure at idle when warmed up. Next, I drained the oil and looked at in the sunlight. It had a gold sparkly glitter material in it when I stirred it up. This was the evidence that made me pull the engine. After disassembly, all the main bearings were severely worn. Especially the ones that were closer to the front of the engine.

So it turns out the oil pressure was reading 60lbs because the wire from the gauge was never hooked to the oil pressure sending unit. Anyway once hooked up it read 40lbs at idle verified with an analog pressure gauge. Anyway the motor turns out to have spun the bearing on number 8 rod. So a new goodwrench tbi engine was purchased and is being installed.