You have to find a correct block with the correct casting number and dates. Then the proper way is to shave the front of the block to remove all the old numbers and then re-stamp with the correct stamps. You can rent the stamps but even that is high. Seems if you shave the front, you may run into issues too but I guess it can be done.

Large cost for nostalgia but legally not numbers matching and can not legally pass off as a numbered matching car.