Nope. Somebody (can't remember who) did a test where they put some Cup 2s on a GT350 Track Pack, and the TP car was still 2 seconds slower than the R. The GT PP2 runs the same Cup 2s, but it's still +/-4 seconds behind the R. Don't discount the aero and suspension tuning. People forget about (or choose to ignore) that all the time.
Forward that if you find it. Obviously depends on the track but 2 sec is a shitload. At VIR that is the dif b/w an FGT and a Zl1 1LE.