Xantia 1.9SD longer 5th gear

[janssensalex10]

Hi everyone

I recently got a Xantia 1.9 SD, absolutely love it but the only issue i have is 3400 rpms at 120 kph on the motorway. When i drive in the Netherlands it goes to 3800 at 130 kmh. Now, i read that the gearbox is the same as the 1.9D NA diesel engine. I want to swap it out for a longer one, but i am not sure which cogs i should get. The longer ratio will be no issue because it has 90 hp now instead of 75

I want to get the revs down to 2500 at 120 kmh

Does anyone have an idea?