If the block is original, it is close to, but not exactly the tractor serial number. A, B, BN, & AV serial numbers were intermixed, so your engine number may be correct for a late '47 B.
There is no other place to find the actual, original tractor serial number.
If you closely look over the major castings, such as the torque tube or transmission you will find numbers cast into them such as 9*25*L. The * will look like a screw head. That is a date code that can tell you when the bigger pieces were cast, giving you and approximate assembly date. If you find one post it and someone on here will look up the year code for you. If the number you find ends in R1, R2, or D, or DA. they are not the numbers you are looking for.