I'm going to post a video of my brothers Int'l Pickup truck. There seems to be a Squeeling noise coming from the back of the motor, the clip describes some of the steps we've taken to fiugure out where the noise is coming from...In addition to these descriptions, we have used carb spray to check for leaks and tried many different combos of carbs and air cleaners. Oh and it is not the throwout bearing.....

My thoughts are that there is a gasket overhang that is causing a "reed" affect....

http://www.youtube.com/watch?v=6bv-qAQS2TA