How flat is that RR anvil? Don't need to be all that flat.
Grind it flat with a side grinder or a belt sander coarse belts.
RR track is a work hardening steel/ Lotta people mess about with heating and quenching them. I don't think it is necessary. On that steel/ If you haven't forged much you might forge on it a bit before you spend time and money flattening the anvil.
It is fun
