take a guess at odd engine noise?

What 4-speed?
The O/Ds have a floating cluster pin, that is supposed to eliminate cluster rattle. Whenever the engine is running and the clutch is not depressed, the maindrive is spinning, and so is the cluster and every other gear inside that box. If the engine is not dead-smooth then the crank is continuously changing speeds. And so is the maindrive and everything else in the box. That is an easy recipe for geartrain rattle. Gear-oil is supposed to suppress that rattle. What oil are you running?
I have to admit, that I doubt your issue is in the tranny.I'm just a post-*****,lol.
But, I have heard alternators make random noises and belts too. Even cam-walk. Certain motorcycles are well known to bounce the cam from one end to the other. Randomly. A timing chain in a chevy can make that racket too. But a Mopar can have really loose chain, and it won't touch the chaincase. Although I have taken some apart that showed evidence of something slapping the case inside there,lol.I've also seen rocker arms slapping a loose baffle in the valve cover.And of course the most common one is an exhaust leak. Or a heatstove. Or a heatriser valve