Casting codes on the engine, transmission, rearend look for something like 5 7 T heres a link http://www.tmtractor.com/id/id_004.htm from TM's site Hope this helps.
Use the casting codes to see if it still has the original engine block. If it is, look for the engine number (below the #1 spark plug). Most Farmall A engine numbers matched the serial numbers. The ones that didn't were all built in 1947.
