I'm not that far in school ATM. I'm only up to Digital II, so I wouldn't know what to do with a PWM... I work for Fairchild Semiconductor, and I know we make PWMs, so if you have a particular PWM to suggest, I can get a whole mess of them for free, and possibly have someone at school (or here) help me integrate it in to the circuit.
One of the things I was wondering about, is that since the 154 has inverted outputs, couldn't I just hook the outputs up to a 7404 inverter to make the outputs going to the LED active high?