I am needing to replace the upper housing on my bravo III drive and I have a bravo I drive also. My question is are the upper housings the same on a bravoI and the Bravo III other than the gear ratio?? thanks in advance.

Basically, yes. Depends on the difference in years between the two. If there is a huge difference in age there could be some issues with oiling. But if they are close in age, they would be the same. Check the drive charts for gear ratio differences.
What are the first two letters in the serial numbers for each?
Hope that helps.
Dick