New guy in Eastern NC

[Recian]

So I'm a first time chevy owner and I've owned imports forever and since I'm buying my first house I needed a bigger truck. My grandad had a 83 silverado diesel and my brother's first car was a 79 scottsdale 3/4 ton so I searched for a square body chevy. I'm now a chevy owner with an 81 Cheyenne. It's got some rust but nothing to serious. No demolished floor pans or severe bed rust. I intend to practice welding body panels since it's just a work truck until my d50 is done.
I'm in the process of figuring out what engine is in the truck. Emissions label says 5.0 but the engine was redone 50k miles ago. Original owner passed, family inherited it and they do alot of racing in the area. They told the guy I bought it from it's a 350 so I think they swapped it. I read 81 should have a 5.0 or 5.7 on the back of the driver head. Serial number on the back of the driver head is 14010202. If anyone knows where I can decode it please let me know.