What greatswords for Forge?
best chance for these 2 are to put in 4 lvl 80 exotic weapons and pray. You can try 4 lvl 80 rares but that chance is very risky since it only a 25% chance to get a exotic greatsword and then add the chance of what type of lvl 80 exotic greatsword you will get makes the chances very low compared to just putting 4 lvl 80 exotics.
However, it may be possible to craft them using specific materials in Mystic Forge but this theory has not been tested yet.