I'm looking for a similar answer. We actually are using letter grades. For the assignment we can award accordingly, but as you stated there are points assigned in the Gradebook. I'm looking forward to anyone who might respond to your request!
I put in this feature request in July, but nothing has happened. I must
point out though that I'm not sure if I posted it correctly 
feature request: http://moodle.org/bugs/bug.php?op=show&bugid=3790&pos=0
original discussion: http://moodle.org/mod/forum/discuss.php?d=27814#131335
cheers
Lindsay
feature request: http://moodle.org/bugs/bug.php?op=show&bugid=3790&pos=0
original discussion: http://moodle.org/mod/forum/discuss.php?d=27814#131335
cheers
Lindsay
I have noticed that the latest updates to 1.5.2 have this feature. I
suggest that you update your version of Moodle to the latest stable
version.
Cheers
Lindsay
Cheers
Lindsay