Weird noise after 4 speed install

BTW
When I had the 292/292/508 Mopar cam, in my 367, it did something like that at 500/550 rpm with the wheels up, LOL.
If you have an aluminum flywheel, or a lightweight flywheel, and a big-for-street, cam, with "too much" idle-timing, then I might consider that racket kindof normal. In my case the engine was just jack-hammering the geartrain. If/when it happens, in first gear, with the idle-rpm pulled right down, then the whole car will get jumpy. And that is real annoying. To solve it, I went to a starter gear of 11/1, and I retard the timing when parading that slow to make the engine pulses less powerful. I have a dash-mounted, dial-back, timing module , with which to do that. It has a range of 15 degrees.
You will soon find out that your Manual trans will NOT like the same ignition timing curve that your Auto did.