There are 61 cars entered in this weekend's Rolex 24 — the biggest field in nearly a decade — including seven in the Prototype class, 10 in LMP2, nine in the LMP3 class, 13 in GTD Pro and 22 in GTD.

At 150 mph, the three different classes of IMSA prototype cars look essentially the same. The top dog is the Daytona Prototype international, or DPi. Second on the rung is the Le Mans Prototype 2, or ...