Clutch "knocking"?

I have what may be a stupid question, but I'm relatively new to owning a 4-speed classic. I know my way around the engine compartment, but the A-833 is a new experience for me. I bought an original 67 Barracuda Fastback 383S 4-speed a little less than a year ago. It came to me with the original trans, but the previous owner had recently installed a new McLeod diaphragm style clutch & throw-out bearing, flywheel was resurfaced, clutch linkage was rebuilt, and the shifter was upgraded to a Hurst Competition plus conversion from the original inland shifter mechanism.

I'm not sure this is a new thing, or if I've just never noticed it before, but when the engine is idling with trans in neutral and the clutch engaged, I hear what I can only describe as a very faint knocking. The sound has no regular pattern, it's just random. It almost sounds like something is loose and rattling, but not severely so. It took me quite a while to determine that it wasn't something loose on the block or an internal engine noise. When I push the clutch pedal in, the noise stops. There is also a distinct sound when I reengage the clutch when it is idling in neutral. The car drives and shifts normally.

Is this sound normal or something I should investigate? Thanks in advance.