Loud Rattling/Tapping between 1,000-1,500 RPMs?

Thanks for the video, it helps. To me it sounds like the exhaust system is contacting the frame somewhere, like a exhaust hanger is broken, or an engine mount is allowing too much movement. I would lift the hood and then have a helper step firmly on the brake pedal with the parking brake well set, then put the truck in drive and give the engine a little throttle. You should be able to see the engine jump upwards indicating a broken engine mount, if it seems okay the other problem can be a broken flex plate which means the transmission will need to come out. We need to locate the source of the noise to get an accurate diagnosis.

You are welcome, please let me know what you find :)

Wow, that sounds way too deep to be a camshaft noise to me. Also, you said the noise does not happen in park or neutral? I am not sure of that diagnosis. :/