I think my 225 is toast

[ame="http://www.youtube.com/watch?v=7zz_3h4quNI&feature=youtu.be"]74 Dart 225 Motor noise - YouTube[/ame]

Bought the car two weeks ago. Has approx 160K on it.

When I run it on the highway, it makes a jackhammering sound from under the hood. The knock stays for a couple of minutes after a highway run, then fades away. As you can see from the video, it's a pretty hard knock on acceleration/sustained high RPM.

Compression is even & good, all plugs are the right brown color. Oil is clean. It does have blowback (some oil in the air cleaner housing).

I have a shake at idle in D (or any gear). Hard shudder through the column & front end on take off, lessens quite a bit in higher gears, not noticeable at all at highway speeds. Trans shifts fine, the flex plate is fine and all bolts are tight. Driveshaft & U-joints are likewise tight. Left mount & trans mount replaced, neither were particularly bad. Valves were adjusted (painted the valve cover then).

I can't tell whether this is a rod knock or some kind of valve train issue. It's loudest at the #6 exhaust manifold neck, but it's really hard to localize (using a mech stethescope). Last (& only) rod knock I had, it did it all the time & never went away.

Thanks for reading & input.

(edit) VV did pull the belts off. The alternator bearings are starting to grate, but it ain't it. :( It is not being driven, this was a short test hop. My son was driving it to work (about 3.5 miles each way, never exceeds 40MPH) but he's using another car now. VV