I could beat this with the R35 TC (6:22.xxx).
If you want my setup pm me and you´ll get it (or I post it here).
I almost won with the Falken GTR.
6:35 was my time and the McLaren did a 6:28 but 7 secs is not managable cause I was on the edge already (maybe 1-2 seconds could go off but still 5 sec gap).
For 2J:
Tranny is important.
First adjust the Topspeed to 350kph-ish (+/+10kph). Then shorten the first gear a bit for a better accel and lenghten the 2nd.
It still has superb accel in the 2nd then but for me it works better.
Suspension:
For Nordschleife I prefer a softer setup and it works fine.
Ride-height: minimal lowering just -2 front and 0 rear for example
Springs: 13.0 front and 13.5-14.0 rear
Damper Extension: 6/6
Damper Compression: 5/5
ARB´s: 4/4
Camber: 2.0/1.5
Toe: -0.22/0.00
Brakebal.: 5/4
Controlersensivity: 7
For me it works like a charme

(my setup is different as above in terms of springs but I´m not near my PS3)