Updated the OP to this point, I went ahead and removed the BMW M6 from the list of cars in favor of the Z4. Also, going to talk about what the calendar will look like.
Confirmed on the calendar:
Okayama International Circuit
Mugello Circuit
Nurburgring 24H
Mount Panorama Motor Racing Circuit Bathurst
Tested Options:
Autodromo Jose Carlos Pace
Autodromo Termas de Rio Hondo
Road America
Circuit of the Americas
Le Circuit Bugatti
Options Yet To Be Tested
Sepang International Circuit
Circuito de Jerez
Bahrain International Circuit
Istanbul Park Circuit
Mazda Raceway Laguna Seca
Circuit de Nevers Magny-Cours
Circuit Paul Ricard
Virginia International Raceway
Circuit Gilles Villeneuve
Points System will be the standard FIA system of 25-18-15-12-10-8-6-4-2-1. Double points will be awarded at the 6 hour events. In addition, at the 6 hour events, all other competitors that make a classified finish get 0.5 points. Points will be awarded to teams, drivers, and manufacturers.
Tire suppliers have been determined to be Michelin, Bridgestone, Dunlop, and Pirelli. The OP will soon be updated with which tire options are available to each car.