The current requirements for a 40x4 backlight are probably 5x that of the nkc LCD, which would put it at the limit of a 1 amp 7805 (and the 2n306 wouldn't handle the current either).
But anyone deviating from the
"official" LCD does so at their own risk. Well, it's all at your own risk really
but there's lots of variables in LCD land and I aint a sorting all that out for everyone. If you know what you are doing, then that's fine, but there's too much else that needs doing for me to hardly mess with it.