As I remember it, trucks rated as a "heavy duty" 1/2 ton or bigger got an emission pass for the 78 model year, but would need to meet emission standards for the 79 model year. I believe all the domestic car manufacturers were allowed to carry the 78 model year on trucks up until the end of Dec 1978. Anything sold after 1/1/1979 had to be a 79 model year and unless it was rated over 4 ton, it needed to meet the 79 emission standards.

Cars didn't get the 78 emission standard "freeze", nor did they get the extended model year. As I understood it, the 440s couldn't meet the "new" emission standards, but the 400 could, so it lived through at least the end of the 78 model year in cars.

I also believe the motor home chassis were purchased in large quantities and carried the year of manufacture for the date they were built into a finished product. I believe if a motor home company had a 440 chassis in stock, they were allowed to sell it up through the end of 1979 mostly because the last Dodge production 440 chassis were built to be over the 4 ton limit.

Also, keep in mind that 78/79 was the time Chrysler went broke the 1st time. The government deal ended Chrysler participation with big trucks, and it ended big blocks. They were allowed to sell whatever was "in stock" but could no longer produce big block stuff.

I was working at a repair shop gas station and we serviced many new vehicles at the time. We had to keep up with the emission standards, even though our area never tested emissions. Gene