I only test the 0-60 of stock cars to compare to the real life times. I got the Corvette Z06 down to 4.4xx secs, vs. the real life 4.2 secs. Never tested any other cars
What I do is run the replay and do a pause-run-pause-run untill I get to 60, and then I take a bit off of that time, like if it was 3.545, then I round it down cause you have to allow the time between when it turned to 60, and when you paused it...