[flatjack9]

Originally Posted by JSeery

A 59 series flathead Ford engine and/or engine block.

From a post by Nate Cooper:

The 59 series blocks had better quality casting control than earlier blocks. This decreased the number of blocks with excessive core shifts. The following boring limitations are what I use for engines intended for the street. The 59 series blocks came in ‘46-’48 Ford and Merc’s. There aren’t any differences between Ford and Merc blocks during these years. All came with replaceable hard valve seats.

There were eight different engine designations to my limited knowledge: 59, 59A, 59AB, 59L, 59X, 59Y, 59Z, and 59ERP. The 59, 59A, and 59AB usually had no factory relief. These are the softest castings of the 59 series blocks. These will almost always bore to 3-3/8″ and still have adequate wall thickness left for street use. These were the most common blocks produced….. which is why they’re also the most common blocks still around today. The raised 59 number and letter (if used) are located on the top of the bell housing.

Not sure the 46-48 year span is totally correct, I have a 59ab that came out of a 49 Truck.

Doubt that that would have been original as Ford used the 8BA blocks starting in 1948.