Try lining up the alternator and anything else that's out of line with the crankshaft pulley. If you shim some things or change some pulleys to make it line up, I bet you your squeal will go away.
A squeal only at 70?
Don't think so.
Maybe a fan pulley under load, but it would do it at about the same rpm in any gear.
Same if it was the alternator doing it.
