Crank fly wheel wobbels until reved.??

What is your question?

Considering buying used 1994 get 5.0 convertible.when idleing crank fly wheel wobbels until reved.is this common or is it possibly bent crank/bad journal's.??

What makes this problem better or worse?

Reving smoothes out.

How long has your 1994 Ford Mustang had this problem?

Not sure car has 94,000 miles