This post is serves mainly to help future persons trying to run Gargoyle on WRT54GL.
I'm trying out Gargoyle for the bandwidth quotas capability.
I installed 1.3.9 as per advice I found in this forum.  However I found 1.3.9 to be very buggy concerning access restrictions.  I didn't even try bandwidth quotas with it because I couldn't get the access restrictions to work.  I tried the suggestions in this post to no avail.  I probably spent about 4 hours trying to get this working on 1.3.9.
So instead I'm using 1.4.7.  I've got access restrictions and bandwidth quotas working it seems.  I've only been running 1.4.7 for a few hours so time will tell if it holds up.  All my tests so far look good.  As others have reported, saving changes can take 3-5 minutes on WRT54GL so patience is required.
Thanks to the developers and volunteers for Gargoyle.  Looks promising.