Engine knock

[fireguyfire]

A buddy of mine has an original 440 in his 1970 mopar.
The engine has been pampered and has seen light duty as a low mile cruiser it's whole like.
It just recently developed a slight bottom end knock and I'm going to help him trouble shoot it, and I wanted to get some opinions on where a guy should look on here.
I'm guessing the likely culprits could be a main bearing, or a rod bearing.
Is there anything else that could lead to a bottom end know?
I'm guessing seeing what's in the oil for metal would be the first step, then drop the pan and try and locate any play.
Can anyone help me out with the best way to troubleshoot a bottom end knock?

[Alaskan_TA]

A loose harmonic balancer can also sound like rod knock.

If it has an automatic transmission and one or more flex plate bolts have backed out, they can hit the webbing at the back of the engine which can also sound like rod knock.

Both of those are very easy to check. 

[fireguyfire]

Great tips, thanks!

[John_Kunkel]

Defective mechanical fuel pump can also produce a slight knock. Use a stethoscope to see if you can isolate the area the noise is coming from.

[Challenger340]

BAD time to be trying to repair/rebuild a 440 Mopar if that turns out to be required ?

LOTS of parts are NLA.... and more stuff going that way weekly post COVID.
* CWC the Camshaft Core Manufacturer that makes the cast Cam Cores for almost everybody.... has served notice that they will NOT be resuming production of BB Mopar Cam Cores(and many other legacy Flat Tappet engines), and current inventories for BB Mopar cams still on the shelf are now pretty much completely depleted everywhere I know of ?
* most Lifters in pretty much anyone "BOX" are just re-Boxed Chinese SHIT LIFTERS.... and causing an epidemic of Cam Lobe failures
* BB Mopar Engine Bearings are getting thin for stock as well ?  CLEVITTE put out a letter in October 2017 that the run done at that time was the end and the CB527P number would be "NLA" in future.... we are still using off that 1700 set "run" of various undersizes....
and
I know your buddy probably isn't looking at anything but as 'stock' type rebuild if that is required(let's hope not).... but if he is just be aware
NO Aluminum Heads available anywhere....
NO Aluminum Intakes left anywhere.....
and on...
and on...