This new series also includes the Shelby GT350R and the Aston Martin Vantage GT3, but if you want to complete it you will need the new Mercedes AMG GT3 upgraded to PR74 (in fact the last four cup races call for PR68/70/72/74).
You can however reach 75% with the Aston.
Other details for the series are:
18 Tiers, 45 events
Gold for Progress 25/50/75/100% = 7/11/16/24 total 58
(If you don't have it, the Mercedes Showcase and TT are unlocked by Tier 9)