Regarding the part number - I am not quite sure and maybe someone out there can help
My car has a build date of November 1969. In the "Hollander" parts interchange manual, two parts are listed - for 440 six pack "Automataic" transmission 1970 challengers.
for "Early" 1970's the part number listed is 2875983
for "Later" 1970's, the part number listed is 3438356
I do not know when the transition point occurred.