Just noticed that the OP was asking specifically about "Large fullblades", not the regular fullblade.
Now, a regular fullblade, converted to 3.5e, is treated as a Large greatsword. So it would logically follow that a Large fullblade (not sure if such a thing can actually exist under raw, but w/e) would logically convert to a Huge greatsword.
Incidentally, this would represent a weapon about 24 feet long. It probably counts as a reach weapon, if you could lift it.
Neither powerful build nor Monkey Grip are of any help with this weapon, as it is two sizes larger than the wielder, and they only help if it is one size larger.
Since it is now a greatsword as the base weapon, there is no EWP for it, although there is of course a MWP for it.
Now, if you had (Powerful Build or Monkey Grip) and were the subject of an enlarge person spell, you could wield that Huge greatsword.