Are you disconnecting the vacuum advance and plugging the vacuum when you are setting the timing?

You probably need to shorten the mechanical advance curve in your distributor so that you can have about 18-20 degrees at idle and about 36 degrees total. These numbers are without the vacuum advance connected. How you do that depends on what distributor you have. Afterwards you can try with and without the vacuum advance connected to see which works best for you.

(edit) I just noticed you are in Denver. That might affect how much timing you need and how much vacuum you are going to get. I don't know but maybe someone else that lives at high altitude can expand on that issue.