Here's the set-up I used for the endurance at The Ring, it'll do 7:11 second laps in my hands (faster in the hands of others, I'm sure) and it's done the endurance in 50:49.431 earning me 62nd on the board. This run was done with tires and damage both off and using only the Auto Transmission assist.
Car Manufacturer and Name: Porsche #44 Flying Lizard
Class: R3
List of Upgrades: N/A
Track: Nürburgring Nordschleife
Car Settings:
Tire Pressure
Front: 28
Rear: 28
Gearing:
F.D.: 4.20
1-5 : Default
6th : 0.92 if using automatic tansmission, default otherwise
Alignment
Camber front: -0.7
Camber Rear: -0.5
Toe Front: 0.0
Toe Rear: -0.5
Front Caster: 5.2
Anti Roll Bars
Front: 18.09
Rear: 12.50
Springs
Front: 329.0
Rear: 473.6
Ride Height
Front: N/A
Rear: N/A
Rebound Damping
Front: 6.0
Rear: 9.0
Bump Stiffness
Front: 3.0
Rear: 4.5
DownForce
Front: 132
Rear: 309
Braking Force
Balance: 49%
Pressure: 95%
Differential
Front Accel: N/A
Front Decel: N/A
Rear Accel: 45%
Rear Decel: 64%
There is some funkyness with 6th gear that makes it sap speed if you change into it. Manual users should not change up to 6th, auto users shouldn't get into 6th (or at least not for long) thanks to the 0.92 ratio on 6th gear.