If it has 1944 on the top of the receiver its not very likely to be from Finland. If it has a small number '44' on the barrel shank along with a [SA] stamp somewhere else on the barrel shank then its likely to be a M39. If not, then its probably a dime-a-dozen russian rifle. If its a Finish rifle, do not drill and tap it,you'd be better off selling it and using the money to buy a Savage or Remington. M39s are usually worth $250-400 depending on which Finish company built them and condition, drilling the receiver will make it into a $100 rifle instantly.
If its a russian rifle, knock yourself out, it'll be a cheap lesson on how expensive sporterizing a surplus rifle really is- best bet is to get a scout mount and a long eye relief scope- much cheaper than smithing the entire rifle and finding out that it won't hit the broad side of a barn because its shot out.