This is my first post, but a long time follower.  I just picked up a 1956 F-600 Dump Truck.  This past weekend I began tearing out the engine and found more rust than expected in the cylinders and heads.  I finally got the engine out and found the Y-Block casting number to be B5AE.  According to the information from my books and websites this is a 272 replacement block.  Can anyone shed some light on what this may be and how it came about? Also one of the heads has a big casted "R" on the deck.  I am guessing that this engine was cobbled together to work on a farm.  Is this a block I should consider keeping or sending it off to the scrap yard??  Any comments are greatly appreciated..

Thanks for keeping the Y-Block Alive and Well...