Time to rebuild?

I know I ticked off SSD and some other experts, but I hate to see people pulling an engine apart when the problem is external to the engine. It is too easy to suggest "just rebuild" at another's expense. Many people start down that path and never finish, leaving a project sitting in the garage for decades, often from frustration. The slant six in my 1969 Dart didn't idle right for decades. Two times mechanics recommended a valve job, which didn't help, I also changed intake manifold, etc looking for a vacuum leak, and ~3 Holley 1920 carburetors, plus had the engine rebuilt. Finally, when it acted the same with an entirely new long block, I tried a 4th carb and bingo it idled like a dream. BTW, that engine swap was necessary as one cylinder had 0 psig compression. Still don't understand how all those "professional" mechanics couldn't solve it. Today, I have more knowledge plus tools like O2 sensors, and avoid all shops. I am the only idiot touching my vehicles today.