VIS higher gear ratio?

Given the torque and free reving of my VIS I often thought it feels low geared, ie it could 'change up' when already in top. What would be the effect of a higher ratio? Would the 6 speed box fit?

To the best of my knowledge you will need to change your steering rack as the 6-speed has an extra part on it. I know folk that have done what you suggest, and yes the VIS "does" feel as if you're needing to change into top when cruising, but it's a lot of labour....

do some gear ratio calc with actual dyno plot to see what effect it will have..

I would change the toothed wheel at 5th gear, otherwise you will damage overall dynamics of the car.. if 6q gearbox, than something from Atmo engine ..or 20VT gearbox with busso 2.5 final drive is the closest ...