95 Chevy C 1500 shortbed regular cab speedy.

Okay, I have a few questions. I am a tech but I have spent most of my time working on Dodge, and Ford vehicles.
According to the specs, I should have 200 hp @ the flywheel for my truck.
So here is a little history on the truck. Friend of mine had a aunt whose husband was dying. So she wanted to sell off his truck. I got it for a steal at $700. She told me that he built it up and he liked to hot rod with it. So I took it for a test drive and my daughter, (who also works on vehicles with me) says “Daddy this engine sounds really good. Like better than any other engine we ever had.” So we are driving and I decided when I got to 40 mph to floor it and see what it did. Tires break loose. We both look at each other and are like both thinking we need to get this truck. So I picked it up for just $700.
Issues with it. It would not start easy on cold days or rainy days. Outside of that, it ran and runs like a champ. I actually get pretty good mileage when I am not hitting the throttle hard. So when I bought it I noticed this little plastic deal with circuits on it that plugged in under my dash. Um okay.
This things is dangerous in the rain. It is so crazy spinning tires, that you cannot but barely drive the thing.
What is under the hood. 350 dual injector throttle body, Dual exhaust. Under the valve covers just normal rockers. Nothing special. Now I had cars running 400 rwhp. which is pretty stout. This guy is not quite in that neighborhood, but he is not that far off. Torque feels awesome. Had a Mustang try to pull road rage on me and drove off really fast so I went after the stang to prove just because you think you got it, it does not mean that the car you just cut off and was a jerk to does not have more. I caught the stang in seconds. My body is not slammed, but it is lowered a little bit. I have 275/40/15 I think they are all around. The thing corners like a race car. I know when I got it the engine was really fresh. Like the guy had maybe 20k on the thing. I put maybe another 20k on it and it is parked. Starts up every time, and once a week or two I drive it around the block a little bit and park it. I am guessing 300-350rwhp maybe? Do you think this guy built up the bottom end in this thing? In Texas for a while there as long as we did not change the appearance of our engine it would pass inspection. Just would like you thoughts on possibilities.
Next. Valve lash adjustment. So the manual says there is no lash adjustment just tighten them to 30 lbs and your good, or something to that extent. So a friend was using my truck after is sat for a year without being driven. I guess I let the oil drain all the way down into the pan a little to long.
So he calls me up and tells me the rockers are tapping or something else. So I pull valve covers off and find the offending rockers. Tighten them up a little bit, and another one would go off on me. So this went on and on until I finally got it nice and quiet. Here is my question. The torque from rocker to rocker was so different in the end it was insane. Again the rotating assembly is super tight and right. So I am thinking this guy just did the bottom end and left the top end. Perhaps I have some worn out tappets or a worn out cam? Cam seems fine, and actually the truck seems fine. Just thinking something is a little off for the torque to be so off. I would say torque is between 15 lbs and 30 lbs.
I would appreciate your input on this. Again it is quiet and running good. Seems like there is no power loss at all. Oh and I have OEM exhaust manifolds, back to a y pipe that sends back to two flowmasters. then two pipes heading out the back. Thanks in advance.