1971 904 transmission questions

[James Camp]

I have a 1971 904 auto transmission in car, has the 904 in large letters on bellhousing close to starter, i have another tranny that looks like a 904, number on passenger side stamped shows come from a 73 model abody but the large numbers in the casting close to starter is 452-2, can anyone tell me what the difference is besides one being 1971 and the other a 1973.

 

[CudaFactHackJob]

Two different fifty years old transmissions. Who knows what somebody did inside of them? And that time frame had running changes. Take them both apart and post pics.