Is the ballast for the g35 coupe the same as the sedan?

YES, they are the same:

Fitment: 2006-2010

Nissan Altima

Nissan Rouge

Nissam Maxima

Nissan Murano

Nissan 350Z

Infiniti FX35 / M35

Infiniti G35 / QX56

Part numbers: NZMNS111LBNA

Replaces Matsushita Ballast