not trying to jack your thread or anything, but I just bought a Kraken too. The guy who sold me it at Cabellas said I could uprgrade it with Tokyo Mauri parts. If our guns are the same then you could do that too. I got the After Math Kraken with some od and clear plastic on it. It shoots 370 fps. Hope it helps.
EDIT: not sure if you wanted to just upgrade the Ak 47 but I guess you wanted to modify it ,changing it into pretty much a whole new gun.