I haven't touched the Protege for a month, since I left it at college while I went home for break. Anyway, I did a little more research on what 5th gears I could put in my Protege.
To covert from engine/model (eg. '00 Protege 1.6L) year info to a Mazdaspeak powertrain (eg. ZM-DE), these articles are useful:
Mazda Z engine - Wikipedia, the free encyclopedia
Mazda B engine - Wikipedia, the free encyclopedia
In Mazdaspeak, my engine is the ZM-DE engine,
Then look at Protege FAQ's article on transmissions...
Protegé FAQ - Transmission Info
According to Protege FAQ, my ZM-DE has an F25M-R transmission. This particular F25M-R has a .775 5th gear and a final drive of 3.850.
There are two American market Proteges with an F25M-R transmission and taller 5th gears:
'92-'94 Protege with B8-ME (1.8L 16V SOHC engine)
5th gear: .731 Final drive: 3.619
'92-'94 MX-3 with B6-E (1.6L 16V SOHC engine)
5th gear: .731 Final drive: 4.05
I think the easiest thing to do would be to find a '92-'94 1.8L SOHC Protege and to swap the 5th gear into my Protege. I don't remember the exact number, but I think my Protege does 3000 rpm at 65mph. The new 5th gear would be 3000*(.731/.775) = 2830 rpm.
Now, I'm debating...is it worth my time to do a gear swap, just to lower my engine speed by 170 rpm?