Hmmm, I should be able to tell you some things about gearboxes, since I amused myself with my 16 v, the 1.9 converted from the 1.6 and the turbo ofcourse !!( also see the story's about them !)
Gears, or ratios are more important than you should think. The use of changing the different ratios is a thing that's has been often underestimated. At the 205 it's really necessary, because gear ratios isn;t Peugeot's best point,... at least not when you want a car that handles like a real machine ! This makes that the 160 BHP 16v in the 205 together with the standard 1.9 gearbox doesn't perform at all. You simply won;t get more than keeping up with the other 16v's on the road (like Gold's and Vauxhalls). And to be honest: I really want more, especially when I paid quite much for the 16v transplant.... I want to crush the stupid Golfs, and only show them my tiny little rear ! Well, it's possible: a very easy solution you can find in using the 1.6 GTi gearbox. This one pulls hard at lower speeds (it revs earlier, especially in the 1st gear where the 1.9 box is tooooo long) but will end quicker, giving a lower top speed. Just for the test: put a 1.9 GTi driver in the same car (1.9) with a 1.6 gearbox and a little wet weather,... result: spinning wheels in the 1st gear ! But,.. after a little searching and some trial- and error we came to the conclusion that a combi-box would be the best choise. That's because the 1.6 box was cool when you wanted to race but on the highway it gave a bit of a nervous making noise, and a top speed to laugh about.

First I'll show you which ratios are available at Peugeot (and Citroen),  so what are the ratios you could make a choise of,.... Speeds are at 6500 rpm,... and than up to the rev-limiter say 250-500 rpm more ! (for the 16v it should be more more more !!!!! (something like 8000 or so !).