Would a cam installed retarded cause the need for excessive initial distributor advance?

We recently fired the 318 in our Duster for the first time. We got it running pretty good and broke in the cam. Now we're getting down to setting everything up. Using the vaccuum method of setting distributor advance, we need to go to 30 degrees initial to get a smooth idle at 900rpm. Anything less and the car will die when put into gear. That seems like way too much initial to me, but maybe not?

We have a Mopar Performance distributor, Summit "small" cam and an Edelbrock 600 carb on an otherwise stock rebuilt 318.

Any thoughts and/or suggestions?
Thanks,
Ken