Possible rod knock?

In my experience, when a rod bearing goes, it is unmistakable;
get under the car and sound the pan.
DO NOT drive the car with a knocking rod, it will only get more expensive.
I have saved my engines several times, by NOT driving it, and rolling in a new bearing. My oilpan has a reusable gasket on it, lol. Zip-Zip, on a hoist, she's in and out in a few hours.
Isolate which cylinder is making the noise, which is usually a double tap, once at each end of travel. I'm gonna say, tucka-tucka-tucka... then Remove the spark from the suspect cylinder. This will reduce the chamber pressure under compression and reduce the volume.
The sound of a loose rod-bearing, to me, cannot be mistaken for any other engine sound. well except maybe a fuel-pump pushrod on engines that have those, NOT SBMs.
However, there are a couple of sounds that can be a close second.
#1) is crankshaft end-play, which is a random sound, coming and going sometimes with no pattern. and
#2) is a loose flexplate which is almost identical to the rodknock, but without the echo of the pan, and it is usually quieter.
#3) I've only ever had one factory flexplate crack on me. It was to me, not of the same volume or intensity, and was missing the reverb of the pan.

to understand the reverb /echo, just tap the oilpan with a light hammer with the engine off. You'll hear it right away.
Endplay is easy to check from underneath
the Flex-plate is a lil more difficult to check,
but hey, you can take solace in knowing that, the metal cover has to usually come off anyway, to remove the oilpan; lol.
I promised myself the last time, that if my Milodon Roadrace oilpan ever had to come off again, I was either taking the engine out, or dropping the K.