Some alarming and unexplained noises my hearse is making

I have a 66 Cadillac hearse that is making a couple alarming noises. The first is a chattering noise that used to be prevalent when I let up on the gas. Now it happens all the time. Someone mentioned I needed a valve job but I don't know if that's it or how much it would cost. Another is a knocking noise coming from under the engine. The 3rd noise is a winding up and down noise that corresponds to how fast I am going and is easiest heard when I am going very slow. Lastly, my brakes make a high pitched screeching noise, but more alarmingly if I stop too fast or am on a hill they make a deep grinding noise. These brakes were just redone less than a year ago. Anyway those are the most pressing things I can think of for now. Thanks!