Tommy Hilfiger, and a 1950 Plymouth; 1948 Dodge; 1948 Chrysler Windsor. And what purpose breather caps?

        I was driving the GMC back from Kennebunkport where it was working on a Tommy Hilfiger fashion shoot. That truck is earning its keep. Somehow--and before I'd dropped off the truck with Tommy's crew--the A/T fluid dipstick got broken. Talk about obscure automotive dilemmas.  So on my way north(east) I planned to check in with Jeff Whitney at Whitney's Automotive in North Windham. They had a bundle of A/T sticks, and though it was a Sunday, Jeff Jr. had agreed to search for one that would fit my truck. 
       Heading north out of Portland on US Route 302, I spied this Mopar trio--a Plymouth, a Dodge, and a Chrysler--in Westbrook, and had to pull over. I would guess the Plymouth is a 1950. The other two a couple years earlier. Correct me if I'm wrong. 
         I retrieved an A/T dipstick at No. Windham, bought a breather oil filler cap at AutoZone in Belfast, and made it home to Brooklin. Opinions on breather caps? Seems to me that the 350 engine burns less oil when I use one.