I need a Chevrolet engines manual

I'm having problems with my pickup truck. A few weeks ago, the cylinder head gaskets were replaced, but it's still fouling one spark plug. I've been told the piston rings might be worn and causing oil to leak. The engine was rebuilt two years ago, but the cylinder heads are the same ones that came with the engine I removed. I converted a 350 to a 305 TBI. Any advice would be helpful. I also need the manuals to reassemble a 350 that I have disassembled. Thanks everyone...

If the spark plug is getting wet with oil, it's either the piston ring or the valve stem seal, but mechanics aren't mind readers, and since they meet in the middle, it's mechanically impossible to know where the oil is coming from. If it's the piston ring, it needs to be adjusted or partially adjusted; that's the only solution