Hummer is no longer an option for RG as GM have dropped the brand all together. He owns a sponsor driven "company" and will race whatever his sponsor pays him to race.
His Hummers this year were an evolution of his previous efforts; lighter & narrower. I expect his next effort to be an expansion of that program.
I wouldn't be surprised to see him in a similarly spec'd Chevy (or Toyota) of some sort as his Hummers really are just custom buggys with body on top.
got me a new 710