I'm trying to determine whether this'54 Chevy has the original differential on it. The engine seems to be winding pretty high in third at 50mph its 2,200rpm.

It has the 235 and standard three-speed with 6.50 16LT tires with full tread. I've tried to make-out the numbers on the diff, even with it all cleaned up I still can't read them. It should be a 3.9 to one ratio if its the original diff.

Anyone have any experience with this?