A903 - which one???

I am pretty sure I have an A903, but it is not original to car. My problem is replacing the input and out put shaft bearings. According to the parts manual, they should be the same bearing. However, they are different. One is an MRC 307 SG17, the other is an MRC 207 S507. I can find the MRC 307 SG17, but not the MRC 207 S507.

If I could figure out the transmission I might have better luck finding the bearing. Besides, I would like to know..... inquiring minds and all that

Omar

I have a '67 slant 6 cuda with 3 on tree