'65 valiant rattling noise - 4spd - 340

Looking to address a rattling noise with this Valiant, it's an A833, 340, 8-3/4" rear. I took it to a shop recently and they couldn't figure out what the cause of the rattle was. It sounds like it's coming from the firewall area. The car starts to rattle around 3k-4k rpm, and you can feel it in the car. It's got an Inland shifter and I noticed the rods are pretty loose on the levers. If I hold the shifter handle it reduces the amount of rattle and noise but not completely. It doesn't rattle sitting still in neutral revving the motor. It does make a slight metallic pinging through the clutch at idle though with the clutch pedal all the way up. If I put some pressure on the clutch pedal (at idle) that slight metallic noise goes away.

Here's a video:


The shop told me it could be spark knock, but I'm not sure, maybe it's just the shifter rods loose on the levers, or maybe something is off with the dowel pins in the bellhousing, or something with the clutch linkage.

The driver's side motor mount is pretty thrashed also. I'm wondering if there's a transmission / motor misalignment.

To get some of the slop out of the shifter, would I start with replacing all the C clips? Would the Hurst shifter bushings be useful on the Inland shifter if those holes or rods have gotten worn out? Or would new rods and levers be worthwhile?

Should I plan a rebuild of all the clutch linkage? What would be the key parts to get for that? Clutch fork, torque shaft, new offset dowel pins?

does it sound like spark knock or not?