You could always make a BCD Encoder for the output of the ADC. As a side-issue, bear in mind that the ADC0801 is designed mainly for use with a microprocessor. That doesn't mean you can't use it as a standalone device - you can and it'll work fine, but you'll want to look up the timing diagrams on the datasheet because you've got to connect it up in a certain way to get it to work on it's own. I managed to figure it out when I used one as a standalone so if you get any problems I'll have a quick look at the datasheet for you - I'm sure I can figure it out again!
Brian