First thing would be to look for a vacuum leak in the flexible lines. A small crack can squeal/whistle loudly. Generally it will be just a hiss. This will make idle rough and difficult as well. On your tear, there are very few. One to look at first is the hose running to your vacuum brake booster (if equipped with power brakes that were and option back then) and the other would be the vacuum advance hose that runs to the vacuum assy on the distributor. Start there, and then (as posted above) a video would be good to help us. The alternator bearings may have dried up and the squeal is a filing bearing, or water pump as well. Change all belts as well to eliminate each possible source. Very doubtful the torque converter would be the cause, but the fluid pump in the front of the trans (you have a power glide 2 speed if stock auto trans) could make noise, but again, rare.