Have you tried a external knock detector or indicator?
I first used a TurboXS knocklite. Worked well as a indicator.
I then installed a J&S Vampire knock controller. it also worked really well even on my engine running forged pistons. IT did a great job when I had a pump pressure issue. Engine was bogging and spitting flames, but the full 10 deg retard due to heavy knock kept the engine together.
There is chap in russia selling a reasonably priced knock indicator using a Bosch knock sensor. You'll be surprised how well such devices work.
Knock is also pretty audible in a car lacking sound insulation. It sounds like sparking. I can be heard even through loud engine noise.
https://www.ebay.de/itm/Knock-contro...19.m1438.l2649
https://youtu.be/vztEn3wLi_c