Squealing noise at 70 mph
 

Fixing up a 67 c1500 pick up. Had a mechanic check the motor and he said all was good. All was good until I got on the freeway and hit 70 mph then I started hearing a squealing noise. Only at when I hit 70 mph!!!!!! WTF!!!! 350 small block with 2 barrel carb oil level, coolant level is good as well as tranny. Any advice would be much appreciated. Thank you!