Rod - I've had bad luck at the bone yards looking for just about everything. There are plenty of OEM HEI distributors at the swap meets but most vendors want WAY too much for them - who knows whether they are servicable or not? If the module is toast, there goes that good deal right out the window...
Aftermarket HEI applications are everywhere. A lot of those are a little over $100, guarentee, adjustable vacume advance, spring kit and all. Personally, that's the way I'd go.