I've been doing some testing for my NASCAR which had a pretty good setup on GT5 and it's around 4 seconds slower with the same settings on GT6. I'm not sure if this is just for NASCAR cars or not, but from my findings a GT5 setup will not give the same results on GT6.
They wont.
however, 'in some cases' you can steal the previous dampers, or lsd. Well, not the decel lsd, that seems to be well off.
but you get what im saying. You can take some things and use them as a base to go from, and then fine tune.