OK. Here is what I'll try.
First, both flash units will work with a Nikon Wireless flash controller, so that should be relatively easy to set up. I've always kind of wanted to try that anyway so I guess this would be a good excuse to blow another $70 on a new toy.
Second, and I should have stated this before, the negatives are definitely underexposed (I worked in a photo lab for 4 years during college as well as doing my own developing and printing in High School). When I started getting the dark prints, the first thing I did was drag out the negs and look at what I had done. The negatives that I have tried to use a bounce flash on are consistantly underexposed. That is the problem. For some reason, weak flash, operator error, etc, I am not properly exposing the prints when trying to use the flash off the ceiling.
I'll try some of the suggestions and let you know.