I believe Pontiac ran into too many problems with their 400 once they added all the pollution controls onto it. They switched to the Olds 403 which didn’t have the same issues.
They were running out of 400 Pontiacs as I recall
When I ordered my 1978 Trans Am, you couldn’t get the Pontiac 400 T/A 6.6 unless with the 4-speed. Mine still came with a Pontiac 400 which had no problems at all.
I was going with the automatic for convience.
1979 Trans Am received the Olds 403 while I think a few were still able to get the T/A 6.6 with a 4-speed.
Ah......the good old days - I miss them - terribly
Mine was one of the last 1978s off the line - Van Nuys assembly I think
If I had waited 2 months I would have gotten a 1979