Ford built a number of tractors with oversized, line bored blocks as Robert says.
They were blocks that had slight faults when originally bored and got oversized and used when stocks got low. I saw a few when in the dealership, they went up to 0.020" O/S I seem to remember. Bearing shells are no longer available but some companies will re-metal your existing shells.
They may also be stamped O/S near the serial number.