You will have to find your own top speed and ride height. There is no conversion from GT3/GT4 to GT5 for ride height that I am aware of. I just try and keep the differences the same. eg. -10 front/-5 back for a ride height of 109/114 in the GTVault tunes.
For Fume's tune, the toe value for the front is +2. Try -0.40 front toe in GT5.
For Vimana's tune, the toe value for the front is -1 and the back +1. Try +0.20 front toe and -0.20 rear toe in GT5.
There are other tunes listed on GTVault that you could try as well.