Matt, you must mean the 902/50 which has a 7:31 R/P. Where do you presume that a 902/55 exists? I cannot find such a transaxle in any of my literature. The 911 workshop manual #1 has this as a 902/50 with a 7:31 R/P just like the sheet above,
If there does exist a 902/55 with A,E,I,O,U gears and it has a 6:29 R/P than it will be geared MUCH lower than the actual 902/50...too low. Do you have data showing this box exists?