Just finished some testing.
Well the gt-r34 has the advantage of race mods but the ctr2 sport is the lighter one. I was thinking ruf turbo r, that one is heavier. Anyway the two cars run on similar specs if you watch closely: the gt-r34 has the 118 hp advantage but the ctr2 sport is lighter with an less 113 kg.
On the track top speeds were similar. I managed to get 4 or 5 extra kph when I removed all the aero support from the gt-r reaching 369.xx kph, with the ctr2 sport I got 367.xx kph.
Both values could be improved, this was basicaly a one run test, but the idea I get is that both cars run almost the same and that 380 kph is probably unachivable, maybe 375/376 max.