I guess it all depends on how "correct" you want to be. The Polish laminate is beautiful in its own right but it really doesn't look like the original Russian. They're both made from different types of wood... I believe the Russians used baltic birch... anyway, the Russian laminate has a reflective appearance to it under the shellac finish they applied. You just don't get that with Polish, Romanian, etc laminate. Is the groove in the stock a must have? Again, that's all relative. I don't think it serves any functional purpose but yes, the 74s had grooves in their stocks.
ETA: It's my understanding that Ironwood Designs makes laminated furniture from the same wood as the Russians used (Baltic Birch?). While I don't really like the looks of their upper and lower handguards, their stocks are pretty nice and can be finished by someone like Z_Recto to look almost identical to a reall Russian stock. They also made them with the grooves in the sides.