Younggun, good for you buying an old DB. What model sedan do you have? The vacuum tank should mount on the passenger side firewall. If you don't have a owner's manual I think the AACA library does. They can copy and send it to you for a few dollars. At the top of this page under "resources" look for the library and go to on line search and type in 1928 Dodge Brothers. You can ask your questions here on down in the DB section.
_________________________
Official member of the L.S.S. I know it's misspelled, they only let me use 16 letters