Problem solved
As per advice from a reply I called Pete at Gould Gear & Electric. He
found it unlikely that it would be the vacuum pump. He had me check
some vacuum lines & the one that was under the battery box going
to the cruise control had deteriorated. I cut out the bad part on
the line, replacing it with a new section and the problem was solved.
I did not need a new vacuum pump, as a Dodge dealership told me.
Thank you Pete and TRD! Bruz