Those breathers were used in 1970 & 71 in California to control evaporative emissions. Chrysler was dirt cheap in their efforts to comply with the standards out here, and believe it or not, any gasoline evaporative fumes from the carburetor bowl were routed through the breather when the engine was shut off and into the engine crankcase. Similarly, any gasoline fumes from the fuel tank were not vented to the atomosphere, they too were routed to the crankcase through the breather! So if your oil smelled always like gasoline, that was the reason. I also heard stories that some cars even on the assembly line no less, had accumulated so much evaporated gasoline, that when the cars were started for the first time, a few blew the oil pans off the engines. Virtually all the other manufacturers used charcoal canisters to capture these evaporative emissions and then sucked them into the engine when it was running to purge the canister.
Chrysler had the worst emission control systems through the 70s and into the early eighties, such as the stupid lean burn that never worked well and the excessive exhaust gas recirculation and no spark advance. Even when catalysts were introduced in 1975, Chrysler engineers didn't know how to utilize them to lower emissions. It was sad and the engineers in charge at the time were only concerned with costs and considered California the land of "fruits and nuts" - who cares if the cars stall repeatedly and don't run right! In the late 70s their stupidity sent them into bankruptcy. Stan is right, the golden years ended really around 1973 and then everything went downhill from there for a long time.